More Hunting Wasps
by
J. Henri Fabre
Part 1 out of 4
This etext was produced by Sue Asscher
MORE HUNTING WASPS
by J. HENRI FABRE
TRANSLATED BY ALEXANDER TEIXEIRA DE MATTOS, F. Z. S.
TRANSLATOR'S NOTE.
The fourteen chapters contained in this volume complete the list of essays
in the "Souvenirs entomologiques" devoted to Wasps. The remainder will be
found in the two earlier volumes of this collected edition entitled "The
Hunting Wasps" and the "Mason-wasps" respectively.
Chapter 2 has appeared before in my version of "The Life and Love of the
Insect," an illustrated volume of extracts translated by myself and
published by Messrs. Adam and Charles Black (in America by the Macmillan
Co.), and Chapter 10 in a similar miscellany translated by Mr. Bernard
Miall published by Messrs. T. Fisher Unwin Ltd. (in America by the Century
Co.) under the title of "Social Life in the Insect World." These two
chapters are included in the present book by arrangement with the original
firms.
I wish to place on record my thanks to Mr. Miall for the valuable
assistance which he has given me in preparing this translation.
ALEXANDER TEIXEIRA DE MATTOS.
Ventnor, I. W., 6 December, 1920.
CONTENTS.
TRANSLATOR'S NOTE.
CHAPTER 1. THE POMPILI.
CHAPTER 2. THE SCOLIAE.
CHAPTER 3. A DANGEROUS DIET.
CHAPTER 4. THE CETONIA-LARVA.
CHAPTER 5. THE PROBLEM OF THE SCOLIAE.
CHAPTER 6. THE TACHYTES.
CHAPTER 7. CHANGE OF DIET.
CHAPTER 8. A DIG AT THE EVOLUTIONISTS.
CHAPTER 9. RATIONING ACCORDING TO SEX.
CHAPTER 10. THE BEE-EATING PHILANTHUS.
CHAPTER 11. THE METHOD OF THE AMMOPHILAE.
CHAPTER 12. THE METHOD OF THE SCOLIAE.
CHAPTER 13. THE METHOD OF THE CALICURGI.
CHAPTER 14. OBJECTIONS AND REJOINDERS.
INDEX.
CHAPTER 1. THE POMPILI. (This essay should be read in conjunction with that
on the Black-bellied Tarantula. Cf. "The Life of the Spider," by J. Henri
Fabre, translated by Alexander Teixeira de Mattos: chapter 1.--Translator's
Note.)
The Ammophila's caterpillar (Cf. "The Hunting Wasps," by J. Henri Fabre,
translated by Alexander Teixeira de Mattos: chapters 13 and 18 to 20; and
Chapter 11 of the present volume.--Translator's Note.), the Bembex (Cf.
idem: chapter 14.--Translator's Note.), Gad-fly, the Cerceris (Cf. idem:
chapters 1 to 3.--Translator's Note.), Buprestis (A Beetle usually
remarkable for her brilliant colouring. Cf. idem: chapter 1.--Translator's
Note.) and Weevil, the Sphex (Cf. idem: chapter 4 to 10.--Translator's
Note.), Locust, Cricket and Ephippiger (Cf. "The Life of the Grasshopper,"
by J. Henri Fabre, translated by Alexander Teixeira de Mattos: chapters 13
and 14.--Translator's Note.): all these inoffensive peaceable victims are
like the silly Sheep of our slaughter-houses; they allow themselves to be
operated upon by the paralyser, submitting stupidly, without offering much
resistance. The mandibles gape, the legs kick and protest, the body
wriggles and twists; and that is all. They have no weapons capable of
contending with the assassin's dagger. I should like to see the huntress
grappling with an imposing adversary, one as crafty as herself, an expert
layer of ambushes and, like her, bearing a poisoned dirk. I should like to
see the bandit armed with her stiletto confronted by another bandit equally
familiar with the use of that weapon. Is such a duel possible? Yes, it is
quite possible and even quite common. On the one hand we have the Pompili,
the protagonists who are always victorious; on the other hand we have the
Spiders, the protagonists who are always overthrown.
Who that has diverted himself, however little, with the study of insects
does not know the Pompili? Against old walls, at the foot of the banks
beside unfrequented footpaths, in the stubble after the harvest, in the
tangles of dry grass, wherever the Spider spreads her nets, who has not
seen them busily at work, now running hither and thither, at random, their
wings raised and quivering above their backs, now moving from place to
place in flights long or short? They are hunting for a quarry which might
easily turn the tables and itself prey upon the trapper lying in wait for
it.
The Pompili feed their larvae solely on Spiders; and the Spiders feed on
any insect, commensurate with their size, that is caught in their nets.
While the first possess a sting, the second have two poisoned fangs. Often
their strength is equally matched; indeed the advantage is not seldom on
the Spider's side. The Wasp has her ruses of war, her cunningly
premeditated strokes: the Spider has her wiles and her set traps; the first
has the advantage of great rapidity of movement, while the second is able
to rely upon her perfidious web; the one has a sting which contrives to
penetrate the exact point to cause paralysis, the other has fangs which
bite the back of the neck and deal sudden death. We find the paralyser on
the one hand and the slaughterer on the other. Which of the two will become
the other's prey?
If we consider only the relative strength of the adversaries, the power of
their weapons, the virulence of their poisons and their different modes of
action, the scale would very often be weighted in favour of the Spider.
Since the Pompilus always emerges victorious from this contest, which
appears to be full of peril for her, she must have a special method, of
which I would fain learn the secret.
In our part of the country, the most powerful and courageous Spider-
huntress is the Ringed Pompilus (Calicurgus annulatus, FAB.), clad in black
and yellow. She stands high on her legs; and her wings have black tips, the
rest being yellow, as though exposed to smoke, like a bloater. Her size is
about that of the Hornet (Vespa crabro). She is rare. I see three or four
of her in the course of the year; and I never fail to halt in the presence
of the proud insect, rapidly striding through the dust of the fields when
the dog-days arrive. Its audacious air, its uncouth gait, its war-like
bearing long made me suspect that to obtain its prey it had to make some
impossible, terrible, unspeakable capture. And my guess was correct. By
dint of waiting and watching I beheld that victim; I saw it in the
huntress' mandibles. It is the Black-bellied Tarantula, the terrible Spider
who slays a Carpenter-bee or a Bumble-bee outright with one stroke of her
weapon; the Spider who kills a Sparrow or a Mole; the formidable creature
whose bite would perhaps not be without danger to ourselves. Yes, this is
the bill of fare which the proud Pompilus provides for her larva.
This spectacle, one of the most striking with which the Hunting Wasps have
ever provided me, has as yet been offered to my eyes but once; and that was
close beside my rural home, in the famous laboratory of the harmas. (The
enclosed piece of waste land on which the author studied his insects in
their native state. Cf. "The Life of the Fly," by J. Henri Fabre,
translated by Alexander Teixeira de Mattos: chapter 1.--Translator's Note.)
I can still see the intrepid poacher dragging by the leg, at the foot of a
wall, the monstrous prize which she had just secured, doubtless at no great
distance. At the base of the wall was a hole, an accidental chink between
some of the stones. The Wasp inspected the cavern, not for the first time:
she had already reconnoitred it and the premises had satisfied her. The
prey, deprived of the power of movement, was waiting somewhere, I know not
where; and the huntress had gone back to fetch it and store it away. It was
at this moment that I met her. The Pompilus gave a last glance at the cave,
removed a few small fragments of loose mortar; and with that her
preparations were completed. The Lycosa (The Spider in question is known
indifferently as the Black-bellied Tarantula and the Narbonne Lycosa.--
Translator's Note.) was introduced, dragged along, belly upwards, by one
leg. I did not interfere. Presently the Wasp reappeared on the surface and
carelessly pushed in front of the hole the bits of mortar which she had
just extracted from it. Then she flew away. It was all over. The egg was
laid; the insect had finished for better or for worse; and I was able to
proceed with my examination of the burrow and its contents.
The Pompilus has done no digging. It is really an accidental hole with
spacious winding passages, the result of the mason's negligence and not of
the Wasp's industry. The closing of the cavity is quite as rough and
summary. A few crumbs of mortar, heaped up before the doorway, form a
barricade rather than a door. A mighty hunter makes a poor architect. The
Tarantula's murderess does not know how to dig a cell for her larva; she
does not know how to fill up the entrance by sweeping dust into it. The
first hole encountered at the foot of a wall contents her, provided that it
be roomy enough; a little heap of rubbish will do for a door. Nothing could
be more expeditious.
I withdraw the game from the hole. The egg is stuck to the Spider, near the
beginning of the belly. A clumsy movement on my part makes it fall off at
the moment of extraction. It is all over: the thing will not hatch; I shall
not be able to observe the development of the larva. The Tarantula lies
motionless, flexible as in life, with not a trace of a wound. In short, we
have here life without movement. From time to time the tips of the tarsi
quiver a little; and that is all. Accustomed of old to these deceptive
corpses, I can see in my mind's eye what has happened: the Spider has been
stung in the region of the thorax, no doubt once only, in view of the
concentration of her nervous system. I place the victim in a box in which
it retains all the pliancy and all the freshness of life from the 2nd of
August to the 20th of September, that is to say, for seven weeks. These
miracles are familiar to us (Cf. "The Hunting Wasps": passim.--Translator's
Note.); there is no need to linger over them here.
The most important matter has escaped me. What I wanted, what I still want
to see is the Pompilus engaged in mortal combat with the Lycosa. What a
duel, in which the cunning of the one has to overcome the terrible weapons
of the other! Does the Wasp enter the burrow to surprise the Tarantula at
the bottom of her lair? Such temerity would be fatal to her. Where the big
Bumble-bee dies an instant death, the audacious visitor would perish the
moment she entered. Is not the other there, facing her, ready to snap at
the back of her head, inflicting a wound which would result in sudden
death? No, the Pompilus does not enter the Spider's parlour, that is
obvious. Does she surprise the Spider outside her fortress? But the Lycosa
is a stay-at-home animal; I do not see her straying abroad during the
summer. Later, in the autumn, when the Pompili have disappeared, She
wanders about; turning gipsy, she takes the open air with her numerous
family, which she carries on her back. Apart from these maternal strolls,
she does not appear to me to leave her castle; and the Pompilus, I should
think, has no great chance of meeting her outside. The problem, we
perceive, is becoming complicated: the huntress cannot make her way into
the burrow, where she would risk sudden death; and the Spider's sedentary
habits make an encounter outside the burrow improbable. Here is a riddle
which would be interesting to decipher. Let us endeavour to do so by
observing other Spider-hunters; analogy will enable us to draw a
conclusion.
I have often watched Pompili of every species on their hunting-expeditions,
but I have never surprised them entering the Spider's lodging when the
latter was at home. Whether this lodging be a funnel plunging its neck into
a hole in some wall, an awning stretched amid the stubble, a tent modelled
upon the Arab's, a sheath formed of a few leaves bound together, or a net
with a guard-room attached, whenever the owner is indoors the suspicious
Pompilus holds aloof. When the dwelling is vacant, it is another matter:
the Wasp moves with arrogant ease over those webs, springes and cables in
which so many other insects would remain ensnared. The silken threads do
not seem to have any hold upon her. What is she doing, exploring those
empty webs? She is watching to see what is happening on the adjacent webs
where the Spider is ambushed. The Pompilus therefore feels an insuperable
reluctance to make straight for the Spider when the latter is at home in
the midst of her snares. And she is right, a hundred times over. If the
Tarantula understands the practice of the dagger-thrust in the neck, which
is immediately fatal, the other cannot be unacquainted with it. Woe then to
the imprudent Wasp who presents herself upon the threshold of a Spider of
approximately equal strength!
Of the various instances which I have collected of this cautious reserve on
the Spider-huntress' part I will confine myself to the following, which
will be sufficient to prove my point. By joining, with silken strands, the
three folioles which form the leaf of Virgil's cytisus, a Spider has built
herself a green arbour, a horizontal sheath, open at either end. A questing
Pompilus comes upon the scene, finds the game to her liking and pops in her
head at the entrance of the cell. The Spider immediately retreats to the
other end. The huntress goes round the Spider's dwelling and reappears at
the other door. Again the Spider retreats, returning to the first entrance.
The Wasp also returns to it, but always by the outside. Scarcely has she
done so, when the Spider rushes for the opposite opening; and so on for
fully a quarter of an hour, both of them coming and going from one end of
the cylinder to the other, the Spider inside and the Pompilus outside.
The quarry was a valuable one, it seems, since the Wasp persisted for a
long time in her attempts, which were invariably defeated; however, the
huntress had to abandon them, baffled by this perpetual running to and fro.
The Pompilus made off; and the Spider, once more on the watch, patiently
awaited the heedless Midges. What should the Wasp have done to capture this
much-coveted game? She should have entered the verdant cylinder, the
Spider's dwelling, and pursued the Spider direct, in her own house, instead
of remaining outside, going from one door to the other. With such swiftness
and dexterity as hers, it seemed to me impossible that the stroke should
fail: the quarry moved clumsily, a little sideways, like a Crab. I judged
it to be an easy matter; the Pompilus thought it highly dangerous. To-day I
am of her opinion: if she had entered the leafy tube, the mistress of the
house would have operated on her neck and the huntress would have become
the quarry.
Years passed and the paralyser of the Spiders still refused to reveal her
secret; I was badly served by circumstances, could find no leisure, was
absorbed in unrelenting preoccupations. At length, during my last year at
Orange, the light dawned upon me. My garden was enclosed by an old wall,
blackened and ruined by time, where, in the chinks between the stones,
lived a population of Spiders, represented more particularly by Segestria
perfidia. This is the common Black Spider, or Cellar Spider. She is deep
black all over, excepting the mandibles, which are a splendid metallic
green. Her two poisoned daggers look like a product of the metal-worker's
art, like the finest bronze. In any mass of abandoned masonry there is not
a quiet corner, not a hole the size of one's finger, in which the Segestria
does not set up house. Her web is a widely flaring funnel, whose open end,
at most a span across, lies spread upon the surface of the wall, where it
is held in place by radiating threads. This conical surface is continued by
a tube which runs into a hole in the wall. At the end is the dining-room to
which the Spider retires to devour at her ease her captured prey.
With her two hind-legs stuck into the tube to obtain a purchase and the six
others spread around the orifice, the better to perceive on every side the
quiver which gives the signal of a capture, the Segestria waits motionless,
at the entrance of her funnel, for an insect to become entangled in the
snare. Large Flies, Drone-flies, dizzily grazing some thread of the snare
with their wings, are her usual victims. At the first flutter of the netted
Fly, the Spider runs or even leaps forward, but she is now secured by a
cord which escapes from the spinnerets and which has its end fastened to
the silken tube. This prevents her from falling as she darts along a
vertical surface. Bitten at the back of the head, the Drone-fly is dead in
a moment; and the Segestria carries him into her lair.
Thanks to this method and these hunting-appliances--an ambush at the bottom
of a silken whirlpool, radiating snares, a life-line which holds her from
behind and allows her to take a sudden rush without risking a fall--the
Segestria is able to catch game less inoffensive than the Drone-fly. A
Common Wasp, they tell me, does not daunt her. Though I have not tested
this, I readily believe it, for I well know the Spider's boldness.
This boldness is reinforced by the activity of the venom. It is enough to
have seen the Segestria capture some large Fly to be convinced of the
overwhelming effect of her fangs upon the insects bitten in the neck. The
death of the Drone-fly, entangled in the silken funnel, is reproduced by
the sudden death of the Bumble-bee on entering the Tarantula's burrow. We
know the effect of the poison on man, thanks to Antoine Duges'
investigations. (Antoine Louis Duges (1797-1838), a French physician and
physiologist, author of a "Traite de physiologie comparee de l'homme et des
animaux" and other scientific works.--Translator's Note.) Let us listen to
the brave experimenter:
"The treacherous Segestria, or Great Cellar Spider, reputed poisonous in
our part of the country, was chosen for the principal subject of our
experiments. She was three-quarters of an inch long, measured from the
mandibles to the spinnerets. Taking her in my fingers from behind, by the
legs, which were folded and gathered together (this is the way to catch
hold of live Spiders, if you would avoid their bite and master them without
mutilating them), I placed her on various objects and on my clothes,
without her manifesting the least desire to do any harm; but hardly was she
laid on the bare skin of my fore-arm when she seized a fold of the
epidermis in her powerful mandibles, which are of a metallic green, and
drove her fangs deep into it. For a few moments she remained hanging,
although left free; then she released herself, fell and fled, leaving two
tiny wounds, a sixth of an inch apart, red, but hardly bleeding, with a
slight extravasation round the edge and resembling the wounds produced by a
large pin.
"At the moment of the bite, the sensation was sharp enough to deserve the
name of pain; and this continued for five or six minutes more, but not so
forcibly. I might compare it with the sensation produced by the stinging-
nettle. A whitish tumefaction almost immediately surrounded the two pricks;
and the circumference, within a radius of about an inch, was coloured an
erysipelas red, accompanied by a very slight swelling. In an hour and a
half, it had all disappeared, except the mark of the pricks, which
persisted for several days, as any other small wound would have done. This
was in September, in rather cool weather. Perhaps the symptoms would have
displayed somewhat greater severity at a warmer season."
Without being serious, the effect of the Segestria's poison is plainly
marked. A sting causing sharp pain and swelling, with the redness of
erysipelas, is no trifling matter. While Duges' experiment reassures us in
so far as we ourselves are concerned, it is none the less the fact that the
Cellar Spider's poison is a terrible thing for insects, whether because of
the small size of the victim, or because it acts with special efficacy upon
an organization which differs widely from our own. One Pompilus, though
greatly inferior to the Segestria in size and strength, nevertheless makes
war upon the Black Spider and succeeds in overpowering this formidable
quarry. This is Pompilus apicalis, VAN DER LIND, who is hardly larger than
the Hive-bee, but very much slenderer. She is of a uniform black; her wings
are a cloudy brown, with transparent tips. Let us follow her in her
expeditions to the old wall inhabited by the Segestria: we will track her
for whole afternoons during the July heats; and we will arm ourselves with
patience, for the perilous capture of the game must take the Wasp a long
time.
The Spider-huntress explores the wall minutely; she runs, leaps and flies;
she comes and goes, flitting to and fro. The antennae quiver; the wings,
raised above the back, continually beat one against the other. Ah, here she
is, close to a Segestria's funnel! The Spider, who has hitherto remained
invisible, instantly appears at the entrance to the tube; she spreads her
six fore-legs outside, ready to receive the huntress. Far from fleeing
before the terrible apparition, she watches the watcher, fully prepared to
prey upon her enemy. Before this intrepid demeanour the Pompilus draws
back. She examines the coveted game, walks round it for a moment, then goes
away without attempting anything. When she has gone, the Segestria retires
indoors, backwards. For the second time the Wasp passes near an inhabited
funnel. The Spider on the lookout at once shows herself on the threshold of
her dwelling, half out of her tube, ready for defence and perhaps also for
attack. The Pompilus moves away and the Segestria reenters her tube. A
fresh alarm: the Pompilus returns; another threatening demonstration on the
part of the Spider. Her neighbour, a little later, does better than this:
while the huntress is prowling about in the neighbourhood of the funnel,
she suddenly leaps out of the tube, with the lifeline which will save her
from falling, should she miss her footing, attached to her spinnerets; she
rushes forward and hurls herself in front of the Pompilus, at a distance of
some eight inches from her burrow. The Wasp, as though terrified,
immediately decamps; and the Segestria no less suddenly retreats indoors.
Here, we must admit, is a strange quarry: it does not hide, but is eager to
show itself; it does not run away, but flings itself in front of the
hunter. If our observations were to cease here, could we say which of the
two is the hunter and which the hunted? Should we not feel sorry for the
imprudent Pompilus? Let a thread of the trap entangle her leg; and it is
all up with her. The other will be there, stabbing her in the throat. What
then is the method which she employs against the Segestria, always on the
alert, ready for defence, audacious to the point of aggression? Shall I
surprise the reader if I tell him that this problem filled me with the most
eager interest, that it held me for weeks in contemplation before that
cheerless wall? Nevertheless, my tale will be a short one.
On several occasions I see the Pompilus suddenly fling herself on one of
the Spider's legs, seize it with her mandibles and endeavour to draw the
animal from its tube. It is a sudden rush, a surprise attack, too quick to
permit the Spider to parry it. Fortunately, the latter's two hind-legs are
firmly hooked to the dwelling; and the Segestria escapes with a jerk, for
the other, having delivered her shock attack, hastens to release her hold;
if she persisted, the affair might end badly for her. Having failed in this
assault, the Wasp repeats the procedure at other funnels; she will even
return to the first when the alarm is somewhat assuaged. Still hopping and
fluttering, she prowls around the mouth, whence the Segestria watches her,
with her legs outspread. She waits for the propitious moment; she leaps
forward, seizes a leg, tugs at it and springs out of reach. More often than
not, the Spider holds fast; sometimes she is dragged out of the tube, to a
distance of a few inches, but immediately returns, no doubt with the aid of
her unbroken lifeline.
The Pompilus' intention is plain: she wants to eject the Spider from her
fortress and fling her some distance away. So much perseverance leads to
success. This time all goes well: with a vigorous and well-timed tug the
Wasp has pulled the Segestria out and at once lets her drop to the ground.
Bewildered by her fall and even more demoralized by being wrested from her
ambush, the Spider is no longer the bold adversary that she was. She draws
her legs together and cowers into a depression in the soil. The huntress is
there on the instant to operate on the evicted animal. I have barely time
to draw near to watch the tragedy when the victim is paralysed by a thrust
of the sting in the thorax.
Here at last, in all its Machiavellian cunning, is the shrewd method of the
Pompilus. She would be risking her life if she attacked the Segestria in
her home; the Wasp is so convinced of it that she takes good care not to
commit this imprudence; but she knows also that, once dislodged from her
dwelling, the Spider is as timid, as cowardly as she was bold at the centre
of her funnel. The whole point of her tactics, therefore, lies in
dislodging the creature. This done, the rest is nothing.
The Tarantula-huntress must behave in the same manner. Enlightened by her
kinswoman, Pompilus apicalis, my mind pictures her wandering stealthily
around the Lycosa's rampart. The Lycosa hurries up from the bottom of her
burrow, believing that a victim is approaching; she ascends her vertical
tube, spreading her fore-legs outside, ready to leap. But it is the Ringed
Pompilus who leaps, seizes a leg, tugs and hurls the Lycosa from her
burrow. The Spider is henceforth a craven victim, who will let herself be
stabbed without dreaming of employing her venomous fangs. Here craft
triumphs over strength; and this craft is not inferior to mine, when,
wishing to capture the Tarantula, I make her bite a spike of grass which I
dip into the burrow, lead her gently to the surface and then with a sudden
jerk throw her outside. For the entomologist as for the Pompilus, the
essential thing is to make the Spider leave her stronghold. After this
there is no difficulty in catching her, thanks to the utter bewilderment of
the evicted animal.
Two contrasting points impress me in the facts which I have just set forth:
the shrewdness of the Pompilus and the folly of the Spider. I will admit
that the Wasp may gradually have acquired, as being highly beneficial to
her posterity, the instinct by which she first of all so judiciously drags
the victim from its refuge, in order there to paralyse it without incurring
danger, provided that you will explain why the Segestria, possessing an
intellect no less gifted than that of the Pompilus, does not yet know how
to counteract the trick of which she has so long been the victim. What
would the Black Spider need to do to escape her exterminator? Practically
nothing: it would be enough for her to withdraw into her tube, instead of
coming up to post herself at the entrance, like a sentry, whenever the
enemy is in the neighbourhood. It is very brave of her, I agree, but also
very risky. The Pompilus will pounce upon one of the legs spread outside
the burrow for defence and attack; and the besieged Spider will perish,
betrayed by her own boldness. This posture is excellent when waiting for
prey. But the Wasp is not a quarry; she is an enemy and one of the most
dreaded of enemies. The Spider knows this. At the sight of the Wasp,
instead of placing herself fearlessly but foolishly on her threshold, why
does she not retreat into her fortress, where the other would not attack
her? The accumulated experience of generations should have taught her this
elementary tactical device, which is of the greatest value to the
prosperity of her race. If the Pompilus has perfected her method of attack,
why has not the Segestria perfected her method of defence? Is it possible
that centuries upon centuries should have modified the one to its advantage
without succeeding in modifying the other? Here I am utterly at a loss. And
I say to myself, in all simplicity: since the Pompili must have Spiders,
the former have possessed their patient cunning and the other their foolish
audacity from all time. This may be puerile, if you like to think it so,
and not in keeping with the transcendental aims of our fashionable
theorists; the argument contains neither the subjective nor the objective
point of view, neither adaptation nor differentiation, neither atavism nor
evolutionism. Very well, but at least I understand it.
Let us return to the habits of Pompilus apicalis. Without expecting results
of any particular interest, for in captivity the respective talents of the
huntress and the quarry seem to slumber, I place together, in a wide jar, a
Wasp and a Segestria. The Spider and her enemy mutually avoid each other,
both being equally timid. A judicious shake or two brings them into
contact. The Segestria, from time to time, catches hold of the Pompilus,
who gathers herself up as best she can, without attempting to use her
sting; the Spider rolls the insect between her legs and even between her
mandibles, but appears to dislike doing it. Once I see her lie on her back
and hold the Pompilus above her, as far away as possible, while turning her
over in her fore-legs and munching at her with her mandibles. The Wasp,
whether by her own adroitness or owing to the Spider's dread of her,
promptly escapes from the terrible fangs, moves to a short distance and
does not seem to trouble unduly about the buffeting which she has received.
She quietly polishes her wings and curls her antennae by pulling them while
standing on them with her fore-tarsi. The attack of the Segestria,
stimulated by my shakes, is repeated ten times over; and the Pompilus
always escapes from the venomous fangs unscathed, as though she were
invulnerable.
Is she really invulnerable? By no means, as we shall soon have proved to
us; if she retires safe and sound, it is because the Spider does not use
her fangs. What we see is a sort of truce, a tacit convention forbidding
deadly strokes, or rather the demoralization due to captivity; and the two
adversaries are no longer in a sufficiently warlike mood to make play with
their daggers. The tranquillity of the Pompilus, who keeps on jauntily
curling her antennae in face of the Segestria, reassures me as to my
prisoner's fate; for greater security, however, I throw her a scrap of
paper, in the folds of which she will find a refuge during the night. She
instals herself there, out of the Spider's reach. Next morning I find her
dead. During the night the Segestria, whose habits are nocturnal, has
recovered her daring and stabbed her enemy. I had my suspicions that the
parts played might be reversed! The butcher of yesterday is the victim of
to-day.
I replace the Pompilus by a Hive-bee. The interview is not protracted. Two
hours later, the Bee is dead, bitten by the Spider. A Drone-fly suffers the
same fate. The Segestria, however, does not touch either of the two
corpses, any more than she touched the corpse of the Pompilus. In these
murders the captive seems to have no other object than to rid herself of a
turbulent neighbour. When appetite awakes, perhaps the victims will be
turned to account. They were not; and the fault was mine. I placed in the
jar a Bumble-bee of average size. A day later the Spider was dead; the rude
sharer of her captivity had done the deed.
Let us say no more of these unequal duels in the glass prison and complete
the story of the Pompilus whom we left at the foot of the wall with the
paralysed Segestria. She abandons her prey on the ground and returns to the
wall. She visits the Spider's funnels one by one, walking on them as freely
as on the stones; she inspects the silken tubes, dipping her antennae into
them, sounding and exploring them; she enters without the least hesitation.
Whence does she now derive the temerity thus to enter the Segestria's
haunts? But a little while ago, she was displaying extreme caution; at this
moment, she seems heedless of danger. The fact is that there is no danger
really. The Wasp is inspecting uninhabited houses. When she dives down a
silken tunnel, she very well knows that there is no one in, for, had the
Segestria been there, she would by this time have appeared on the
threshold. The fact that the householder does not show herself at the first
vibration of the neighbouring threads is a certain proof that the tube is
vacant; and the Pompilus enters in full security. I would recommend future
observers not to take the present investigations for hunting-tactics. I
have already remarked and I repeat: the Pompilus never enters the silken
ambush while the Spider is there.
Among the funnels inspected one appears to suit her better than the others;
she returns to it frequently in the course of her investigations, which
last for nearly an hour. From time to time she hastens back to the Spider
lying on the ground; she examines her, tugs at her, drags her a little
closer to the wall, then leaves her the better to reconnoitre the tunnel
which is the object of her preference. Lastly she returns to the Segestria
and takes her by the tip of the abdomen. The quarry is so heavy that she
has great difficulty in moving it along the level ground. Two inches divide
it from the wall. She gets to the wall, not without effort; nevertheless,
once the wall is reached, the job is quickly done. We learn that Antaeus,
the son of Mother Earth, in his struggle with Hercules, received new
strength as often as his feet touched the ground; the Pompilus, the
daughter of the wall, seems to increase her powers tenfold once she has set
foot on the masonry.
For here is the Wasp hoisting her prey backwards, her enormous prey, which
dangles beneath her. She climbs now a vertical plane, now a slope,
according to the uneven surface of the stones. She crosses gaps where she
has to go belly uppermost, while the quarry swings to and fro in the air.
Nothing stops her; she keeps on climbing, to a height of six feet or more,
without selecting her path, without seeing her goal, since she goes
backwards. A lodge appears no doubt reconnoitred beforehand and reached,
despite the difficulties of an ascent which did not allow her to see it.
The Pompilus lays her prey on it. The silken tube which she inspected so
lovingly is only some eight inches distant. She goes to it, examines it
rapidly and returns to the Spider, whom she at length lowers down the tube.
Shortly afterwards I see her come out again. She searches here and there on
the wall for a few scraps of mortar, two or three fairly large pieces,
which she carries to the tube, to close it up. The task is done. She flies
away.
Next day I inspect this strange burrow. The Spider is at the bottom of the
silken tube, isolated on every side, as though in a hammock. The Wasp's egg
is glued not to the ventral surface of the victim but to the back, about
the middle, near the beginning of the abdomen. It is white, cylindrical and
about a twelfth of an inch long. The few bits of mortar which I saw carried
have but very roughly blocked the silken chamber at the end. Thus Pompilus
apicalis lays her quarry and her eggs not in a burrow of her own making,
but in the Spider's actual house. Perhaps the silken tube belongs to this
very victim, which in that event provides both board and lodging. What a
shelter for the larva of this Pompilus: the warm retreat and downy hammock
of the Segestria!
Here then, already, we have two Spider-huntresses, the Ringed Pompilus and
P. apicalis, who, unversed in the miner's craft, establish their offspring
inexpensively in accidental chinks in the walls, or even in the lair of the
Spider on whom the larva feeds. In these cells, acquired without exertion,
they build only an attempt at a wall with a few fragments of mortar. But we
must beware of generalizing about this expeditious method of establishment.
Other Pompili are true diggers, valiantly sinking a burrow in the soil, to
a depth of a couple of inches. These include the Eight-spotted Pompilus (P.
octopunctatus, PANZ.), with her black-and-yellow livery and her amber
wings, a little darker at the tips. For her game she chooses the Epeirae
(E. fasciata, E. sericea) (For the Garden-spiders known as the Banded
Epeira and the Silky Epeira cf. "The Life of the Spider": chapters 11, 13,
14 et passim.--Translator's Note.), those fat Spiders, magnificently
adorned, who lie in wait at the centre of their large, vertical webs. I am
not sufficiently acquainted with her habits to describe them; above all, I
know nothing of her hunting-tactics. But her dwelling is familiar to me: it
is a burrow, which I have seen her begin, complete and close according to
the customary method of the Digger-wasps.
CHAPTER 2. THE SCOLIAE.
Were strength to take precedence over the other zoological attributes, the
Scoliae would hold a predominant place in the front rank of the Wasps. Some
of them may be compared in size with the little bird from the north, the
Golden-crested Wren, who comes to us at the time of the first autumn mists
and visits the rotten buds. The largest and most imposing of our sting-
bearers, the Carpenter-bee, the Bumble-bee, the Hornet, cut a poor figure
beside certain of the Scoliae. Of this group of giants my district
possesses the Garden Scolia (S. hortorum, VAN DER LIND), who is over an
inch and a half in length and measures four inches from tip to tip of her
outspread wings, and the Hemorrhoidal Scolia (S. haemorrhoidalis, VAN DER
LIND), who rivals the Garden Scolia in point of size and is distinguished
more particularly by the bundle of red hairs bristling at the tip of the
abdomen.
A black livery, with broad yellow patches; leathery wings, amber-coloured,
like the skin of an onion, and watered with purple reflections; thick,
knotted legs, covered with sharp hairs; a massive frame; a powerful head,
encased in a hard cranium; a stiff, clumsy gait; a low, short, silent
flight: this gives you a concise description of the female, who is strongly
equipped for her arduous task. The male, being a mere philanderer, sports a
more elegant pair of horns, is more daintily clad and has a more graceful
figure, without altogether losing the quality of robustness which is his
consort's leading characteristic.
It is not without a certain alarm that the insect-collector finds himself
for the first time confronted by the Garden Scolia. How is he to capture
the imposing creature, how to avoid its sting? If its effect is in
proportion to the Wasp's size, the sting of the Scolia must be something
terrible. The Hornet, though she unsheath her weapon but once, causes the
most exquisite pain. What would it be like if one were stabbed by this
colossus? The prospect of a swelling as big as a man's fist and as painful
as the touch of a red-hot iron passes through our mind at the moment when
we are bringing down the net. And we refrain, we beat a retreat, we are
greatly relieved not to have aroused the dangerous creature's attention.
Yes, I confess to having run away from my first Scoliae, anxious though I
was to enrich my budding collection with this magnificent insect. There
were painful recollections of the Common Wasp and the Hornet connected with
this excess of prudence. I say excess, for to-day, instructed by long
experience, I have quite recovered from my former fears; and, when I see a
Scolia resting on a thistle-head, I do not scruple to take her in my
fingers, without any precaution whatever, however large she may be and
however menacing her aspect. My courage is not all that it seems to be; I
am quite ready to tell the Wasp-hunting novice this. The Scoliae are
notably peaceable. Their sting is an implement of labour far more than a
weapon of war; they use it to paralyse the prey destined for their
offspring; and only in the last extremity do they employ it in self-
defence. Moreover, the lack of agility in their movements nearly always
enables us to avoid their sting; and, even if we be stung, the pain is
almost insignificant. This absence of any acute smarting as a result of the
poison is almost constant in the Hunting Wasps, whose weapon is a surgical
lancet and devised for the most delicate physiological operations.
Among the other Scoliae of my district I will mention the Two-banded Scolia
(S. bifasciata, VAN DER LIND), whom I see every year, in September, working
at the heaps of leaf-mould which are placed for her benefit in a corner of
my paddock; and the Interrupted Scolia (S. interrupta, LATR.), the
inhabitant of the sandy soil at the foot of the neighbouring hills. Much
smaller than the two preceding insects, but also much commoner, a necessary
condition of continuous observation, they will provide me with the
principal data for this study of the Scoliae.
I open my old note book; and I see myself once more, on the 6th of August,
1857, in the Bois des Issards, that famous copse near Avignon which I have
celebrated in my essay on the Bembex-wasps. (Cf. "The Hunting Wasps":
chapter 14.--Translator's Note.) Once again, my head crammed with
entomological projects, I am at the beginning of my holidays which, for two
months, will allow me to indulge in the insect's company.
A fig for Mariotte's flask and Toricelli's tube! (Edme Mariotte (1620-
1684), a French chemist who discovered, independently of Robert Boyle the
Irishman (1627-1691), the law generally known as Boyle's law, which states
that the product of the volume and the temperature of a gas is constant at
constant temperature. His flask is an apparatus contrived to illustrate
atmospheric pressure and ensure a constant flow of liquid.--Translator's
Note.) (Evangelista Toricelli (1608-1647), a disciple of Galileo and
professor of philosophy and mathematics at Florence. His "tube" is our
mercury barometer. He was the first to obtain a vacuum by means of mercury;
and he also improved the microscope and the telescope.--Translator's Note.)
This is the thrice-blest period when I cease to be a schoolmaster and
become a schoolboy, the schoolboy in love with animals. Like a madder-
cutter off for his day's work, I set out carrying over my shoulder a solid
digging-implement, the local luchet, and on my back my game-bag with boxes,
bottles, trowel, glass tubes, tweezers, lenses and other impedimenta. A
large umbrella saves me from sunstroke. It is the most scorching hour of
the hottest day in the year. Exhausted by the heat, the Cicadae are
silent. The bronze-eyed Gad-flies seek a refuge from the pitiless sun under
the roof of my silken shelter; other large Flies, the sobre-hued Pangoniae,
dash themselves recklessly against my face.
The spot at which I have installed myself is a sandy clearing which I had
recognized the year before as a site beloved of the Scoliae. Here and there
are scattered thickets of holm-oak, whose dense undergrowth shelters a bed
of dead leaves and a thin layer of mould. My memory has served me well.
Here, sure enough, as the heat grows a little less, appear, coming I know
not from whence, some Two-banded Scoliae. The number increases; and it is
not long before I see very nearly a dozen of them about me, close enough
for observation. By their smaller size and more buoyant flight, they are
easily known for males. Almost grazing the ground, they fly softly, going
to and fro, passing and repassing in every direction. From time to time one
of them alights on the ground, feels the sand with his antennae and seems
to be enquiring into what is happening in the depths of the soil; then he
resumes his flight, alternately coming and going.
What are they waiting for? What are they seeking in these evolutions of
theirs, which are repeated a hundred times over? Food? No, for close beside
them stand several eryngo-stems, whose sturdy clusters are the Wasps' usual
resource at this season of parched vegetation; and not one of them settles
upon the flowers, not one of them seems to care about their sugary
exudations. Their attention is engrossed elsewhere. It is the ground, it is
the stretch of sand which they are so assiduously exploring; what they are
waiting for is the arrival of some female, who bursting the cocoon, may
appear from one moment to the next, issuing all dusty from the ground. She
will not be given time to brush herself or to wash her eyes: three or four
more of them will be there at once, eager to dispute her possession. I am
too familiar with the amorous contests of the Hymenopteron clan to allow
myself to be mistaken. It is the rule for the males, who are the earlier of
the two, to keep a close guard around the natal spot and watch for the
emergence of the females, whom they pester with their pursuit the moment
they reach the light of day. This is the motive of the interminable ballet
of my Scoliae. Let us have patience: perhaps we shall witness the nuptials.
The hours go by; the Pangoniae and the Gad-flies desert my umbrella; the
Scoliae grow weary and gradually disappear. It is finished. I shall see
nothing more to-day. I repeat my laborious expedition to the Bois des
Issards over and over again; and each time I see the males as assiduous as
ever in skimming over the ground. My perseverance deserved to succeed. It
did, though the success was very incomplete. Let me describe it, such as it
was; the future will fill up the gaps.
A female issues from the soil before my eyes. She flies away, followed by
several males. With the luchet I dig at the point of emergence; and, as the
excavation progresses, I sift between my fingers the rubbish of sand mixed
with mould. In the sweat of my brow, as I may justly say, I must have
removed nearly a cubic yard of material, when at last I make a find. This
is a recently ruptured cocoon, to the side of which adheres an empty skin,
the last remnant of the game on which the larva fed that wrought the said
cocoon. Considering the good condition of its silken fabric, this cocoon
may have belonged to the Scolia who has just quitted her underground
dwelling before my eyes. As for the skin accompanying it, this has been so
much spoilt by the moisture of the soil and by the grassy roots that I
cannot determine its origin exactly. The cranium, however, which is better-
preserved, the mandibles and certain details of the general configuration
lead me to suspect the larva of a Lamellicorn.
It is getting late. This is enough for to-day. I am worn out, but amply
repaid for my exertions by a broken cocoon and the puzzling skin of a
wretched grub. Young people who make a hobby of natural history, would you
like to discover whether the sacred fire flows in your veins? Imagine
yourselves returning from such an expedition. You are carrying on your
shoulder the peasant's heavy spade; your loins are stiff with the laborious
digging which you have just finished in a crouching position; the heat of
an August afternoon has set your brain simmering; your eyelids are tired by
the itch of an inflammation resulting from the overpowering light in which
you have been working; you have a devouring thirst; and before you lies the
dusty prospect of the miles that divide you from your well-earned rest. Yet
something stings within you; forgetful of your present woes you are
absolutely glad of your excursion. Why? Because you have in your possession
a shred of rotten skin. If this is so, my young friends, you may go ahead,
for you will do something, though I warn you that this does not mean, by a
long way, that you will get on in the world.
I examined this shred of skin with all the care that it deserved. My first
suspicions were confirmed: a Lamellicorn, a Scarabaeid in the larval state,
is the first food of the Wasp whose cocoon I have just unearthed. But which
of the Scarabaeidae? And does this cocoon, my precious booty, really belong
to the Scoliae? The problem is beginning to take shape. To attempt its
solution we must go back to the Bois des Issards.
I did go back and so often that my patience ended by being exhausted before
the problem of the Scoliae had received a satisfactory solution. The
difficulties are great indeed, under the conditions. Where am I to dig in
the indefinite stretch of sandy soil to light upon a spot frequented by the
Scoliae? The luchet is driven into the ground at random; and almost
invariably I find none of what I am seeking. To be sure, the males, flying
level with the ground, give me a hint, at the outset, with their certainty
of instinct, as to the spots where the females ought to be; but their hints
are very vague, because they go so far in every direction. If I wished to
examine the soil which a single male explores in his flight, with its
constantly changing course, I should have to turn over, to the depth of
perhaps a yard, at least four poles of earth. This is too much for my
strength and the time at my disposal. Then, as the season advances, the
males disappear, whereupon I am suddenly deprived of their hints. To know
more or less where I should thrust my luchet, I have only one resource
left, which is to watch for the females emerging from the ground or else
entering it. With a great expenditure of time and patience I have at last
had this windfall, very rarely, I admit.
The Scoliae do not dig a burrow which can be compared with that of the
other Hunting Wasps; they have no fixed residence, with an unimpeded
gallery opening on the outer world and giving access to the cells, the
abodes of the larvae. They have no entrance- and exit-doors, no corridor
built in advance. If they have to make their way underground, any point not
hitherto turned over serves their purpose, provided that it be not too hard
for their digging-tools, which, for that matter, are very powerful; if they
have to come out, the point of exit is no less indifferent. The Scolia does
not bore the soil through which she passes: she excavates and ploughs it
with her legs and forehead; and the stuff shifted remains where it lies,
behind her, forthwith blocking the passage which she has followed. When she
is about to emerge into the outer world, her advent is heralded by the
fresh soil which heaps itself into a mound as though heaved up by the snout
of some tiny Mole. The insect sallies forth; and the mound collapses,
completely filling up the exit-hole. If the Wasp is entering the ground,
the digging-operations, undertaken at an arbitrary point, quickly yield a
cavity in which the Scolia disappears, separated from the surface by the
whole track of shifted material.
I can easily trace her passage through the thickness of the soil by certain
long, winding cylinders, formed of loose materials in the midst of compact
and stable earth. These cylinders are numerous; they sometimes run to a
depth of twenty inches; they extend in all directions, fairly often
crossing one another. Not one of them ever exhibits so much as a suspicion
of an open gallery. They are obviously not permanent ways of communication
with the outer world, but hunting-trails which the insect has followed
once, without going back to them. What was the Wasp seeking when she
riddled the soil with these tunnels which are now full of running sands? No
doubt the food for her family, the larva of which I possess the empty skin,
now an unrecognizable shred.
I begin to see a little light: the Scoliae are underground workers. I
already expected as much, having before now captured Scoliae soiled with
little earthy encrustations on the joints of the legs. The Wasp, who is so
careful to keep clean, taking advantage of the least leisure to brush and
polish herself, could never display such blemishes unless she were a
devoted earth-worker. I used to suspect their trade, now I know it. They
live underground, where they burrow in search of Lamellicorn-grubs, just as
the Mole burrows in search of the White Worm. (The larva of the Cockchafer.
This grub takes three years or more to arrive at maturity underground.--
Translator's Note.) It is even possible that, after receiving the embraces
of the males, they but very rarely return to the surface, absorbed as they
are by their maternal duties; and this, no doubt, is why my patience
becomes exhausted in watching for their entrance and their emergence.
It is in the subsoil that they establish themselves and travel to and fro;
with the help of their powerful mandibles, their hard cranium, their
strong, prickly legs, they easily make themselves paths in the loose earth.
They are living ploughshares. By the end of August, therefore, the female
population is for the most part underground, busily occupied in egg-laying
and provisioning. Everything seems to tell me that I should watch in vain
for the appearance of a few females in the broad daylight; I must resign
myself to excavating at random.
The result was hardly commensurate with the labour which I expended on
digging. I found a few cocoons, nearly all broken, like the one which I
already possessed, and, like it, bearing on their side the tattered skin of
a larva of the same Scarabaeid. Two of these cocoons which are still intact
contained a dead adult Wasp. This was actually the Two-banded Scolia, a
precious discovery which changed my suspicions into a certainty.
I also unearthed some cocoons, slightly different in appearance, containing
an adult inmate, likewise dead, in whom I recognized the Interrupted
Scolia. The remnants of the provisions again consisted of the empty skin of
a larva, also a Lamellicorn, but not the same as the one hunted by the
first Scolia. And this was all. Now here, now there, I shifted a few cubic
yards of soil, without managing to find fresh provisions with the egg or
the young larva. And yet it was the right season, the egg-laying season,
for the males, numerous at the outset, had grown rarer day by day until
they disappeared entirely. My lack of success was due to the uncertainty of
my excavations, in which I had nothing to guide me over the indefinite area
covered.
If I could at least identify the Scarabaeidae whose larvae form the prey of
the two Scoliae, the problem would be half solved. Let us try. I collect
all that the luchet has turned up: larvae, nymphs and adult Beetles. My
booty comprises two species of Lamellicorns: Anoxia villosa and Euchlora
Julii, both of whom I find in the perfect state, usually dead, but
sometimes alive. I obtain a few of their nymphs, a great piece of luck, for
the larval skin which accompanies them will serve me as a standard of
comparison. I come upon plenty of larvae, of all ages. When I compare them
with the cast garment abandoned by the nymphs, I recognize some as
belonging to the Anoxia and the rest to the Euchlora.
With these data, I perceive with absolute certainty that the empty skin
adhering to the cocoon of the Interrupted Scolia belongs to the Anoxia. As
for the Euchlora, she is not involved in the problem: the larva hunted by
the Two-banded Scolia does not belong to her any more than it belongs to
the Anoxia. Then with which Scarabaeid does the empty skin which is still
unknown to me correspond? The Lamellicorn whom I am seeking must exist in
the ground which I have been exploring, because the Two-banded Scolia has
established herself there. Later--oh, very long afterwards!--I recognized
where my search was at fault. In order not to find a network of roots
beneath my luchet and to render the work of excavation lighter, I was
digging the bare places, at some distance from the thickets of holm-oak;
and it was just in those thickets, which are rich in vegetable mould, that
I should have sought. There, near the old stumps, in the soil consisting of
dead leaves and rotting wood, I should certainly have come upon the larva
so greatly desired, as will be proved by what I have still to say.
Here ends what my earlier investigations taught me. There is reason to
believe that the Bois des Issards would never have furnished me with the
precise data, in the form in which I wanted them. The remoteness of the
spot, the fatigue of the expeditions, which the heat rendered intensely
exhausting, the impossibility of knowing which points to attack would
undoubtedly have discouraged me before the problem had advanced a step
farther. Studies such as these call for home leisure and application, for
residence in a country village. You are then familiar with every spot in
your own grounds and the surrounding country and you can go to work with
certainty.
Twenty-three years have passed; and here I am at Serignan, where I have
become a peasant, working by turns on my writing-pad and my cabbage-patch.
On the 14th of August, 1880, Favier (An ex-soldier who acted as the
author's gardener and factotum.--Translator's Note.) clears away a heap of
mould consisting of vegetable refuse and of leaves stacked in a corner
against the wall of the paddock. This clearance is considered necessary
because Bull, when the lovers' moon arrives, uses this hillock to climb to
the top of the wall and thence to repair to the canine wedding the news of
which is brought to him by the effluvia borne upon the air. His pilgrimage
fulfilled, he returns, with a discomfited look and a slit ear, but always
ready, once he has had his feed, to repeat the escapade. To put an end to
this licentious behaviour, which has cost him so many gaping wounds, we
decided to remove the heap of soil which serves him as a ladder of escape.
Favier calls me while in the midst of his labours with the spade and
barrow:
"Here's a find, sir, a great find! Come and look."
I hasten to the spot. The find is a magnificent one indeed and of a nature
to fill me with delight, awakening all my old recollections of the Bois des
Issards. Any number of females of the Two-banded Scolia, disturbed at their
work, are emerging here and there from the depth of the soil. The cocoons
also are plentiful, each lying next to the skin of the victim on which the
larva has fed. They are all open but still fresh: they date from the
present generation; the Scoliae whom I unearth have quitted them not long
since. I learnt later, in fact, that the hatching took place in the course
of July.
In the same heap of mould is a swarming colony of Scarabaeidae in the form
of larvae, nymphs and adult insects. It includes the largest of our
Beetles, the common Rhinoceros Beetle, or Oryctes nasicornis. I find some
who have been recently liberated, whose wing-cases, of a glossy brown, now
see the sunlight for the first time; I find others enclosed in their
earthen shell, almost as big as a Turkey's egg. More frequent is her
powerful larva, with its heavy paunch, bent into a hook. I note the
presence of a second bearer of the nasal horn, Oryctes Silenus, who is much
smaller than her kinswoman, and of Pentodon punctatus, a Scarabaeid who
ravages my lettuces.
But the predominant population consists of Cetoniae, or Rosechafers, most
of them enclosed in their egg-shaped shells, with earthen walls encrusted
with dung. There are three different species: C. aurata, C. morio and C.
floricola. Most of them belong to the first species. Their larvae, which
are easily recognized by their singular talent for walking on their backs
with their legs in the air, are numbered by the hundred. Every age is
represented, from the new born grub to the podgy larva on the point of
building its shell.
This time the problem of the victuals is solved. When I compare the larval
slough sticking to the Scolia's cocoons with the Cetonia-larvae or, better,
with the skin cast by these larvae, under cover of the cocoon, at the
moment of the nymphal transformation, I establish an absolute identity. The
Two-banded Scolia rations each of her eggs with a Cetonia-grub. Behold the
riddle which my irksome searches in the Bois des Issards had not enabled me
to solve. To-day, at my threshold, the difficult problem becomes child's
play. I can investigate the question easily to the fullest possible extent;
I need not put myself out at all; at any hour of the day, at any period
that seems favourable, I have the requisite elements before my eyes. Ah,
dear village, so poor, so countrified, how happily inspired was I when I
came to ask of you a hermit's retreat, where I could live in the company of
my beloved insects and, in so doing, set down not too unworthily a few
chapters of their wonderful history!
According to the Italian observer Passerini, the Garden Scolia feeds her
family on the larvae of Oryctes nasicornis, in the heaps of old tan-waste
removed from the hot-houses. I do not despair of seeing this colossal Wasp
coming to establish herself one day in my heaps of leaf-mould, in which the
same Scarabaeid is swarming. Her rarity in my part of the country is
probably the only cause that has hitherto prevented the realization of my
wishes.
I have just shown that the Two-banded Scolia feeds in infancy on Cetonia-
larvae and particularly on those of C. aurata, C. morio and C. floricola.
These three species dwell together in the rubbish-heap just explored; their
larvae differ so little that I should have to examine them minutely to
distinguish the one from the other; and even then I should not be certain
of succeeding. It seems probable that the Scolia does not choose between
them, that she uses all three indiscriminately. Perhaps she even assails
other larvae, inhabitants, like the foregoing, of heaps of rotting
vegetable-matter. I therefore set down the Cetonia genus generally as
forming the prey of the Two-banded Scolia.
Lastly, round about Avignon, the Interrupted Scolia used to prey upon the
larva of the Shaggy Anoxia (A. villosa). At Serignan, which is surrounded
by the same kind of sandy soil, without other vegetation than a few sparse
seed-bearing grasses, I find her rationing her young with the Morning
Anoxia (A. matutinalis). Oryctes, Cetoniae and Anoxiae in the larval state:
here then is the prey of the three Scoliae whose habits we know. The three
Beetles are Lamellicorns, Scarabaeidae. We shall have occasion later to
consider the reason of this very striking coincidence.
For the moment, the business in hand is to move the heap of leaf-mould to
some other place, with the wheelbarrow. This is Favier's work, while I
myself collect the disturbed population in glass jars, in order to put them
back into the new rubbish-heap with all the consideration which my plans
owe to them. The laying-time has not yet set in, for I find no eggs, no
young Scolia-larvae. September apparently will be the propitious month. But
there are bound to be many injured in the course of this upheaval; some of
the Scoliae have flown away who will perhaps have a certain difficulty in
finding the new site; I have disarranged everything in the overturned heap.
To allow tranquility to be restored and habit to resume its rounds, to give
the population time to increase and replace the fugitives and the injured,
it would be best, I think, to leave the heap alone this year and not to
resume my investigations until the next. After the thorough confusion due
to the removal, I should jeopardize success by being too precipitate. Let
us wait one year more. I decide accordingly, curb my impatience and resign
myself. We will simply confine ourselves to enlarging the heap, when the
leaves begin to fall, by accumulating the refuse that strews the paddock,
so that we may have a richer field of operations.
In the following August, my visits to the mound of leaf-mould become a
daily habit. By two o'clock in the afternoon, when the sun has cleared the
adjacent pine-trees and is shining on the heap, numbers of male Scoliae
arrive from the neighbouring fields, where they have been slaking their
thirst on the eryngo-heads. Incessantly coming and going with an indolent
flight, they circle round the heap. If some female rise from the soil,
those who have seen her dart forward. A not very turbulent affray decides
which of the suitors shall be the possessor; and the couple fly away over
the wall. This is a repetition of what I used to see in the Bois des
Issards. By the time that August is over. The males have ceased to show
themselves. The mothers do not appear either: they are busy underground,
establishing their families.
On the 2nd of September, I decide upon a search with my son Emile, who
handles the fork and the shovel, while I examine the clods dug up. Victory!
A magnificent result, finer than any that my fondest ambition would have
dared to contemplate! Here is a vast array of Cetonia-larvae, all flaccid,
motionless, lying on their backs, with a Scolia's egg sticking to the
centre of their abdomen; here are young Scolia-larvae dipping their heads
into the entrails of their victims; here are others farther advanced,
munching their last mouthfuls of a prey which is drained dry and reduced to
a skin; here are some laying the foundation of their cocoons with a reddish
silk, which looks as if it had been dyed in Bullock's blood; here are some
whose cocoons are finished. There is plenty of everything, from the egg to
the larva whose period of activity is over. I mark the 2nd of September as
a red-letter day; it has given me the final key to a riddle which has kept
me in suspense for nearly half a century.
I place my spoils religiously in shallow, wide-mouthed glass jars
containing a layer of finely sifted mould. In this soft bed, which is
identical in character with the natal surroundings, I make some faint
impressions with my fingers, so many cavities, each of which receives one
of my subjects, one only. A pane of glass covers the mouth of the
receptacle. In this way I prevent a too rapid evaporation and keep my
nurselings under my eyes without fear of disturbing them. Now that all this
is in order, let us proceed to record events.
The Cetonia-larvae which I find with a Scolia's egg upon their ventral
surface are distributed in the mould at random, without special cavities,
without any sign of some sort of structure. They are smothered in the
mould, just as are the larvae which have not been injured by the Wasp. As
my excavations in the Bois des Issards told me, the Scolia does not prepare
a lodging for her family; she knows nothing of the art of cell-building.
Her offspring occupies a fortuitous abode, on which the mother expends no
architectural pains. Whereas the other Hunting Wasps prepare a dwelling to
which the provisions are carried, sometimes from a distance, the Scolia
confines herself to digging her bed of leaf-mould until she comes upon a
Cetonia-larva. When she finds a quarry, she stabs it on the spot, in order
to immobilize it; and, again on the spot, she lays an egg on the ventral
surface of the paralysed creature. That is all. The mother goes in quest of
another prey without troubling further about the egg which has just been
laid. There is no effort of carting or building. At the very spot where the
Cetonia-grub is caught and paralysed, the Scolia-larva hatches, grows and
weaves its cocoon. The establishment of the family is thus reduced to the
simplest possible expression.
CHAPTER 3. A DANGEROUS DIET.
The Scolia's egg is in no way exceptional in shape. It is white,
cylindrical, straight and about four millimetres long by one millimetre
thick. (About .156 x .039 inch.--Translator's Note.) It is fixed, by its
fore-end, upon the median line of the victim's abdomen, well to the rear of
the legs, near the beginning of the brown patch formed by the mass of food
under the skin.
I watch the hatching. The grub, still wearing upon its hinder parts the
delicate pellicle which it has just shed, is fixed to the spot to which the
egg itself adhered by its cephalic extremity. A striking spectacle, that of
the feeble creature, only this moment hatched, boring, for its first
mouthful, into the paunch of its enormous prey, which lies stretched upon
its back. The nascent tooth takes a day over the difficult task. Next
morning the skin has yielded; and I find the new-born larva with its head
plunged into a small, round, bleeding wound.
In size the grub is the same as the egg, whose dimensions I have just
given. Now the Cetonia-larva, to meet the Scolia's requirements, averages
thirty millimetres in length by nine in thickness (1.17 x .35 inch.--
Translator's Note.), whence follows that its bulk is six or seven hundred
times as great as that of the newly-hatched grub of the Scolia. Here
certainly is a quarry which, were it active and capable of wriggling and
biting, would expose the nurseling to terrible attacks. The danger has been
averted by the mother's stiletto; and the fragile grub attacks the
monster's paunch with as little hesitation as though it were sucking the
breast.
Day by day the young Scolia's head penetrates farther into the Cetonia's
belly. To pass through the narrow orifice made in the skin, the fore-part
of the body contracts and lengthens out, as though drawn through a die-
plate. The larva thus assumes a rather strange form. Its hinder half, which
is constantly outside the victim's belly, has the shape and fulness usual
in the larvae of the Digger-wasps, whereas the front half, which, once it
has dived under the skin of the exploited victim, does not come out again
until the time arrives for spinning the cocoon, tapers off suddenly into a
snake-like neck. This front part is moulded, so to speak, by the narrow
entrance-hole made in the skin and henceforth retains its slender
formation. As a matter of fact, a similar configuration recurs, in varying
degrees, in the larvae of the Digger-wasps whose ration consists of a bulky
quarry which takes a long time to consume. These include the Languedocian
Sphex, with her Ephippiger, and the Hairy Ammophila, with her Grey Worm.
There is none of this sudden constriction, dividing the creature into two
disparate halves, when the victuals consist of numerous and comparatively
small items. The larva then retains its usual shape, being obliged to pass,
at brief intervals, from one joint in its larder to the next.
>From the first bite of the mandibles, until the whole head of game is
consumed, the Scolia-larva is never seen to withdraw its head and its long
neck from inside the creature which it is devouring. I suspect the reason
of this persistence in attacking a single point; I even seem to perceive
the need for a special art in the manner of eating. The Cetonia-larva is a
square meal in itself, one large dish, which has to retain a suitable
freshness until the end. The young Scolia, therefore, must attack with
discretion, at the unvarying point chosen by the mother on the ventral
surface, for the entrance-hole is at the exact point where the egg was
fixed. As the nurseling's neck lengthens and dives deeper, the victim's
entrails are nibbled gradually and methodically: first, the least
essential; next, those whose removal leaves yet a remnant of life; lastly,
those whose loss inevitably entails death, followed very soon by
putrefaction.
At the first bites we see the victim's blood oozing through the wound. It
is a highly-elaborated fluid, easy of digestion, and forms a sort of milk-
diet for the new-born grub. The little ogre's teat is the bleeding paunch
of the Cetonia-larva. The latter will not die of the wound, at least not
for some time. The next thing to be tackled is the fatty substance which
wraps the internal organs in its delicate folds. This again is a loss which
the Cetonia can suffer without dying then and there. Now comes the turn of
the muscular layer which lines the skin; now, that of the essential organs;
now, that of the nerve-centres and the trachean network, whereupon the last
gleam of light is extinguished and the Cetonia reduced to a mere bag, empty
but intact, save for the entrance-hole made in the middle of the belly.
>From now onwards, these remains may rot if they will: the Scolia, by its
methodical fashion of consuming its victuals, has succeeded in keeping them
fresh to the very last; and now you may see it, replete, shining with
health, withdraw its long neck from the bag of skin and prepare to weave
the cocoon in which its development will be completed.
It is possible that I may not be quite accurate as to the precise order in
which the organs are consumed, for it is not easy to perceive what happens
inside the exploited larva's body. The ruling feature in this scientific
method of eating, which proceeds from the parts less to the parts more
necessary to preserve a remnant of life, is none the less obvious. If
direct observation did not already to some degree confirm it, a mere
examination of the half-eaten larva would do so in the most positive
fashion.
The Cetonia-larva is at first a plump grub. Drained by the Scolia's tooth,
it gradually becomes limp and wrinkled. In a few days' time it resembles a
shrivelled bit of bacon-fat and then a bag whose two sides have fallen in.
Yet this bit of bacon and this bag have the same characteristic look of
fresh meat as had the grub before it was bitten into. Despite the
persistent nibbling of the Scolia, life continues, holding at bay the
inroads of putrefaction until the mandibles have given their last bites.
Does not this remnant of tenacious vitality in itself show that the organs
of primary importance are the last to be attacked? Does it not prove that
there is a progressive dismemberment passing from the less essential to the
indispensable?
Would you like to see what becomes of a Cetonia-larva when the organism is
wounded in its vital centres at the very beginning? The experiment is an
easy one; and I made a point of trying it. A sewing-needle, first softened
and flattened into a blade, then retempered and sharpened, gives me a most
delicate scalpel. With this instrument I make a fine incision, through
which I remove the mass of nerves whose remarkable structure we shall soon
have occasion to study. The thing is done: the wound, which does not look
serious, has left the creature a corpse, a real corpse. I lay my victim on
a bed of moist earth, in a jar with a glass lid; in fact, I establish it in
the same conditions as those of the larvae on which the Scoliae feed. By
the next day, without changing shape, it has turned a repulsive brown;
presently it dissolves into noisome putrescence. On the same bed of earth,
under the same glass cover, in the same moist, warm atmosphere, the larvae
three-quarters eaten by the Scoliae retain, on the contrary, the appearance
of healthy flesh.
If a single stroke of my dagger, fashioned from the point of a needle,
results in immediate death and early putrefaction; if the repeated bites of
the Scolia gut the creature's body and reduce it almost to a skin without
completely killing it, the striking contrast between these two results must
be due to the relative importance of the organs injured. I destroy the
nerve-centres and inevitably kill my larva, which is putrid by the
following day; the Scolia attacks the reserves of fat, the blood, the
muscles and does not kill its victim, which will provide it with wholesome
food until the end. But it is clear that, if the Scolia were to set to work
as I did, there would be nothing left, after the first few bites, but an
actual corpse, discharging fluids which would be fatal to it within twenty-
four hours. The mother, it is true, in order to assure the immobility of
her prey, has injected the poison of her sting into the nerve-centres. Her
operation cannot be compared with mine in any respect. She practises the
method of the skilful physiologist who induces anaesthesia; I go to work
like the butcher who chops, cuts and disembowels. The sting leaves the
nerve-centres intact. Deprived of sensibility by the poison, they have lost
the power of provoking muscular contractions; but who can say that, numbed
as they are, they no longer serve to maintain a faint vitality? The flame
is extinguished, but there is still a glowing speck upon the wick. I, a
rough blunderer, do more than blow out the lamp: I throw away the wick and
all is over. The grub would do the same if it bit straight into the mass of
nerves.
Everything confirms the fact: the Scolia and the other Hunting Wasps whose
provisions consist of bulky heads of game are gifted with a special art of
eating, an exquisitely delicate art which saves a remnant of life in the
prey devoured, until it is all consumed. When the prey is a small one, this
precaution is superfluous. Consider, for instance, the Bembex-grubs in the
midst of their heap of Flies. The prey seized upon is broached on the back,
the belly, the head, the thorax, indifferently. The larva munches a given
spot, which it leaves to munch a second, passing to a third and a fourth,
at the bidding of its changing whims. It seems to taste and select, by
repeated trials, the mouthfuls most to its liking. Thus bitton at several
points, covered with wounds, the Fly is soon a shapeless mass which would
putrefy very quickly if the meagre dish were not devoured at a single meal.
Allow the Scolia-grub the same unlicensed gluttony: it would perish beside
its corpulent victim, which should have kept fresh for a fortnight, but
which almost from the beginning would be no more than a filthy putrescence.
This art of careful eating does not seem easy to practise: at least, the
larva, if ever so little diverted from its usual courses, is no longer able
to apply its talent as a capable trencherman. This will be proved by
experiment. I must begin by observing that, when I spoke of my larva which
turned putrid within twenty-four hours, I adopted an extreme case for the
sake of greater clearness. The Scolia, taking its first bite, does not and
cannot go to such lengths. Nevertheless it behooves us to enquire whether,
in the consumption of the victuals, the initial point of attack is a matter
of indifference and whether the rummaging through the entrails of the
victim entails a determined order, without which success is uncertain or
even impossible. To these delicate questions no one, I think, can reply.
Where science is silent, perhaps the grub will speak. We will try.
I move from its position a Scolia-grub which has attained a quarter or a
third of its full growth. The long neck plunged into the victim's belly is
rather difficult to extract, because of the need of molesting the creature
as little as possible. I succeed, by means of a little patience and
repeated strokes with the tip of a paint-brush. I now turn the Cetonia-
larva over, back uppermost, at the bottom of the little hollow made by
pressing my finger in the layer of mould. Lastly, I place the Scolia on its
victim's back. Here is my grub under the same conditions as just now, with
this difference, that the back and not the belly of its victim is presented
to its mandibles.
I watch it for a whole afternoon. It writhes about; it moves its little
head now in this direction, now in that, frequently laying it on the
Cetonia, but without fixing it anywhere. The day draws to a close; and
still it has accomplished nothing. There are restless movements, nothing
more. Hunger, I tell myself, will eventually induce it to bite. I am wrong.
Next morning I find it more anxious than the day before and still groping
about, without resolving to fix its mandibles anywhere. I leave it alone
for half a day longer without obtaining any result. Yet twenty-four hours
of abstinence must have awakened a good appetite, above all in a creature
which, if left undisturbed, would not have ceased eating.
Excessive hunger cannot induce it to nibble at an unlawful spot. Is this
due to feebleness of the teeth? By no means: the Cetonia's skin is no
tougher on the back than on the belly; moreover, the grub is capable of
perforating the skin when it leaves the egg; a fortiori, it must be more
capable of doing so now that it has attained a sturdy growth. Thus we see
no lack of ability, but an obstinate refusal to nibble at a point which
ought to be respected. Who knows? On this side perhaps the grub's dorsal
vessel would be wounded, its heart, an organ indispensable to life. The
fact remains that my attempts to make the grub tackle its victim from the
back have failed. Does this mean that it entertains the least suspicion of
the danger which it might incur were it to produce putrefaction by
awkwardly carving its victuals from the back? It would be absurd to give
such an idea a moment's consideration. Its refusal is dictated by a
preordained decree which it is bound to obey.
My Scolia-grubs would die of starvation if I left them on their victim's
back. I therefore restore matters as they were, with the Cetonia-larva
belly uppermost and the young Scolia on top. I might utilise the subjects
of my previous experiments; but, as I have to take precautions against the
disturbance which may have been caused by the test already undergone, I
prefer to operate on new patients, a luxury in which the richness of my
menagerie allows me to indulge. I move the Scolia from its position,
extract its head from the entrails of the Cetonia-larva and leave it to its
own resources on its victim's belly. Betraying every symptom of uneasiness,
the grub gropes, hesitates, casts about and does not insert its mandibles
anywhere, though it is now the ventral surface which it is exploring. It
would not display greater hesitation if placed on the back of the larva. I
repeat, who knows? On this side it might perhaps injure the nervous plexus,
which is even more essential than the dorsal vessel. The inexperienced grub
must not drive in its mandibles at random; its future is jeopardized if it
gives a single ill-judged bite. If it gnaws at the spot where I myself
operated with my needle wrought into a scalpel, its victuals will very soon
turn putrid. Once more, then, we witness an absolute refusal to perforate
the skin of the victim elsewhere than at the very point where the egg was
fixed.
The mother selects this point, which is undoubtedly that most favourable to
the future prosperity of the larva, though I am not able clearly to discern
the reasons for her choice; she fixes the egg to it; and the place where
the opening is to be made is henceforth determined. It is here that the
grub must bite: only here, never elsewhere. Its invincible refusal to
tackle the Cetonia in any other part, even though it should die of
starvation, shews us how rigorous is the rule of conduct with which its
instinct is inspired.
As it gropes about, the grub laid on the victim's ventral surface sooner or
later rediscovers the gaping wound from which I have removed it. If this
takes too long for my patience, I can myself guide its head to the place
with the point of a paint-brush. The grub then recognizes the hole of its
own making, slips its neck into it and little by little dives into the
Cetonia's belly, so that the original state of affairs appears to be
exactly restored. And yet its successful rearing is henceforth highly
problematical. It is possible that the larva will prosper, complete its
development and spin its cocoon; it is also possible--and the case is not
unusual--that the Cetonia-larva will soon turn brown and putrid. We then
see the Scolia itself turn brown, distended as it is with putrescent
foodstuffs, and then cease all movement, without attempting to withdraw
from the sanies. It dies on the spot, poisoned by its excessively high
game.
What can be the meaning of this sudden corruption of the victuals, followed
by the death of the Scolia, when everything appeared to have returned to
its normal condition? I see only one explanation. Disturbed in its
activities and diverted from its usual courses by my interference, the
grub, when replaced on the wound from which I extracted it, was unable to
rediscover the lode at which it was working a few minutes earlier; it
thrust its way at random into the victim's entrails; and a few untimely
bites extinguished the last sparks of vitality. Its confusion rendered it
clumsy; and the mistake cost it its life. It dies poisoned by the rich food
which, if consumed according to the rules, should have made it grow plump
and lusty.
I was anxious to observe the deadly effects of a disturbed meal in another
fashion. This time the victim itself shall disorder the grub's activities.
The Cetonia-larva, as served up to the young Scolia by its mother, is
profoundly paralysed. Its inertia is complete and so striking that it
constitutes one of the leading features of this narrative. But we will not
anticipate. For the moment, the thing is to substitute for this inert larva
a similar larva, but one not paralysed, one very much alive. To ensure that
it shall not double up and crush the grub, I confine myself to reducing it
to helplessness, leaving it otherwise just as I extracted it from its
burrow. I must also be careful of its legs and mandibles, the least touch
of which would rip open the nurseling. With a few turns of the finest wire
I fix it to a little slab of cork, with its belly in the air. Next, to
provide the grub with a ready-made hole, knowing that it will refuse to
make one for itself, I contrive a slight incision in the skin, at the point
where the Scolia lays her egg. I now place the grub upon the larva, with
its head touching the bleeding wound, and lay the whole on a bed of mould
in a transparent beaker protected by a pane of glass.
Unable to move, to wriggle, to scratch with its legs or snap with its
mandibles, the Cetonia-larva, a new Prometheus bound, offers its
defenceless flanks to the little Vulture destined to devour its entrails.
Without too much hesitation, the young Scolia settles down to the wound
made by my scalpel, which to the grub represents the wound whence I have
just removed it. It thrusts its neck into the belly of its prey; and for a
couple of days all seems to go well. Then, lo and behold, the Cetonia turns
putrid and the Scolia dies, poisoned by the ptomaines of the decomposing
game! As before, I see it turn brown and die on the spot, still half inside
the toxic corpse.
The fatal issue of my experiment is easily explained. The Cetonia-larva is
alive in every sense. True, I have, by means of bonds, suppressed its
outward movements, in order to provide the nurseling with a quiet meal,
devoid of danger; but it was not in my power to subdue its internal
movements, the quivering of the viscera and muscles irritated by its forced
immobility and by the Scolia's bites. The victim is in possession of its
full power of sensation; and it expresses the pain experienced as best it
may, by contractions. Embarrassed by these tremors, these twitches of
suffering flesh, incommoded at every mouthful, the grub chews away at
random and kills the larva almost as soon as it has started on it. In a
victim paralysed by the regulation sting, the conditions would be very
different. There are no external movements, nor any internal movements
either, when the mandibles bite, because the victim is insensible. The
grub, undisturbed in any way, is then able, with an unfaltering tooth, to
pursue its scientific method of eating.
These marvellous results interested me too much not to inspire me with
fresh devices when I pursued my investigations. Earlier enquiries had
taught me that the larvae of the Digger-wasps are fairly indifferent to the
nature of the game, though the mother always supplies them with the same
diet. I had succeeded in rearing them on a great variety of prey, without
paying regard to their normal fare. I shall return to this subject later,
when I hope to demonstrate its great philosophical significance. Let us
profit by these data and try to discover what happens when we give the
Scolia food which is not properly its own.
I select from my heap of garden-mould, that inexhaustible mine, two larvae
of the Rhinoceros Beetle, Oryctes nasicornis, about one-third full-grown,
so that their size may not be out of proportion to the Scolia's. It is in
fact almost identical with the size of the Cetonia. I paralyse one of them
by giving an injection of ammonia in the nerve-centres. I make a fine
incision in its belly and I place the Scolia on the opening. The dish
pleases my charge; and it would be strange indeed if this were not so,
considering that another Scolia-grub, the larva of the Garden Scolia, feeds
on the Oryctes. The dish suits it, for before long it has burrowed half-way
into the succulent paunch. This time all goes well. Will the rearing be
successful? Not a bit of it! On the third day, the Oryctes decomposes and
the Scolia dies. Which shall we hold responsible for the failure, myself or
the grub? Myself who, perhaps too unskilfully, administered the injection
of ammonia, or the grub which, a novice at dissecting a prey differing from
its own, did not know how to practise its craft upon a changed victim and
began to bite before the proper time?
In my uncertainty, I try again. This time I shall not interfere, so that my
clumsiness cannot be to blame. As I described when speaking of the Cetonia-
larva, the Oryctes-larva now lies bound, quite alive, on a strip of cork.
As usual, I make a small opening in the belly, to entice the grub by means
of a bleeding wound and facilitate its access. I obtain the same negative
result. In a little while, the Oryctes is a noisome mass on which the
nurseling lies poisoned. The failure was foreseen: to the difficulties
presented by a prey unknown to my charge was added the commotion caused by
the wriggling of an unparalysed animal.
We will try once more, this time with a victim paralysed not by me, an
unskilled operator, but by an adept whose ability ranks so high that it is
beyond discussion. Chance favours me to perfection: yesterday, in a warm
sheltered corner, at the foot of a sandy bank, I discovered three cells of
the Languedocian Sphex, each with its Ephippiger and the recently laid egg.
This is the game I want, a corpulent prey, of a size suited to the Scolia
and, what is more, in splendid condition, artistically paralysed according
to rule by a master among masters.
As usual, I install my three Ephippigers in a glass jar, on a bed of mould;
I remove the egg of the Sphex and on each victim, after slightly incising
the skin of the belly, I place a young Scolia-grub. For three or four days
my charges feed upon this game, so novel to them, without any sign of
repugnance or hesitation. By the fluctuations of the digestive canal I
perceive that the work of nutrition is proceeding as it should; things are
happening just as if the dish were a Cetonia-larva. The change of diet,
complete though it is, has in no way affected the appetite of the Scolia-
grubs. But this prosperous condition does not last long. About the fourth
day, a little sooner in one case, a little later in another, the three
Ephippigers become putrid and the Scoliae die at the same time.
This result is eloquent. Had I left the egg of the Sphex to hatch, the
larva coming out of it would have fed upon the Ephippiger; and for the
hundredth time I should have witnessed an incomprehensible spectacle, that
of an animal which, devoured piecemeal for nearly a fortnight, grows thin
and empty, shrivels up and yet retains to the very end the freshness
peculiar to living flesh. Substitute for this Sphex-larva a Scolia-larva of
almost the same size; let the dish be the same though the guest is
different; and healthy live flesh is promptly replaced by pestilent rotten
flesh. That which under the mandibles of the Sphex would for a long while
have remained wholesome food promptly becomes a poisonous liquescence under
the mandibles of the Scolia.
It is impossible to explain the preservation of the victuals until finally
consumed by supposing that the venom injected by the Wasp when she delivers
her paralysing stings possesses antiseptic properties. The three
Ephippigers were operated on by the Sphex. Able to keep fresh under the
mandibles of the Sphex-larvae, why did they promptly go bad under the
mandibles of the Scolia-larvae? Any idea of an antiseptic must needs be
rejected: a liquid preservative which would act in the first case could not
fail to act in the second, as its virtues would not depend on the teeth of
the consumer.
Those of you who are versed in the knowledge attaching to this problem,
investigate, I beg you, search, sift, see if you can discover the reason
why the victuals keep fresh when consumed by a Sphex, whereas they promptly
become putrid when consumed by a Scolia. For me, I see only one reason; and
I very much doubt whether any one can suggest another.
Both larvae practise a special art of eating, which is determined by the
nature of the game. The Sphex, when sitting down to an Ephippiger, the food
that has fallen to its lot, knows thoroughly how to consume it and how to
preserve, to the very end, the glimmer of life which keeps it fresh; but,
if it has to browse upon a Cetonia-grub, whose different structure would
confuse its talents as a dissector, it would soon have nothing before it
but a heap of putrescence. The Scolia, in its turn, is familiar with the
method of eating the Cetonia-grub, its invariable portion; but it does not
understand the art of eating the Ephippiger, though the dish is to its
taste. Unable to dissect this unknown species of game, its mandibles slash
away at random, killing the creature outright as soon as they take their
first bites of the deeper tissues of the victim. That is the whole secret.
One more word, on which I shall enlarge in another chapter. I observe that
the Scoliae to which I give Ephippigers paralysed by the Sphex keep in
excellent condition, despite the change of diet, so long as the provisions
retain their freshness. They languish when the game goes high; and they die
when putridity supervenes. Their death, therefore, is due not to an
unaccustomed diet, but to poisoning by one or other of those terrible
toxins which are engendered by animal corruption and which chemistry calls
by the name of ptomaines. Therefore, notwithstanding the fatal outcome of
my three attempts, I remain persuaded that the unfamiliar method of rearing
would have been perfectly successful had the Ephippigers not gone bad, that
is, if the Scoliae had known how to eat them according to the rules.
What a delicate and dangerous thing is the art of eating in these
carnivorous larvae supplied with a single victim, which they have to spend
a fortnight in consuming, on the express condition of not killing it until
the very end! Could our physiological science, of which, with good reason,
we are so proud, describe, without blundering, the method to be followed in
the successive mouthfuls? How has a miserable grub learnt what our
knowledge cannot tell us? By habit, the Darwinians will reply, who see in
instinct an acquired habit.
Before deciding this serious matter, I will ask you to reflect that the
first Wasp, of whatever kind, that thought of feeding her progeny on a
Cetonia-grub or on any other large piece of game demanding long
preservation could necessarily have left no descendants unless the art of
consuming food without causing putrescence had been practised, with all its
scrupulous caution, from the first generation onwards. Having as yet learnt
nothing by habit or by atavistic transmission, since it was making a first
beginning, the nurseling would bite into its provender at random. It would
be starving, it would have no respect for its prey. It would carve its
joint at random; and we have just seen the fatal consequence of an ill-
directed bite. It would perish--I have just proved this in the most
positive manner--it would perish, poisoned by its victim, already dead and
putrid.
To prosper, it would have, although a novice, to know what was permitted
and what forbidden in ransacking the creature's entrails; nor would it be
enough for the larva to be approximately in possession of this difficult
secret: it would be indispensable that it should possess the secret
completely, for a single bite, if delivered before the right moment, would
inevitably involve its own demise. The Scoliae of my experiments are not
novices, far from it: they are the descendants of carvers that have
practised their art since Scoliae first came into the world; nevertheless
they all perish from the decomposition of the rations supplied, when I try
to feed them on Ephippigers paralysed by the Sphex. Very expert in the
method of attacking the Cetonia, they do not know how to set about the
business of discreetly consuming a species of game new to them. All that
escapes them is a few details, for the trade of an ogre fed on live flesh
is familiar to them in its general features; and these unheeded details are
enough to turn their food into poison. What, then, happened in the
beginning, when the larva bit for the first time into a luscious victim?
The inexperienced creature perished; of that there is not a shadow of
doubt, unless we admit an absurdity and imagine the larva of antiquity
feeding upon those terrible ptomaines which so swiftly kill its descendants
to-day.
Nothing will ever make me admit and no unprejudiced mind can admit that
what was once food has become a horrible poison. What the larva of
antiquity ate was live flesh and not putrescence. Nor can it be admitted
that the chances of fortune can have led at the first trial to success in a
system of nourishment so full of pit-falls: fortuitous results are
preposterous amid so many complications. Either the feeding is strictly
methodical at the beginning, in conformity with the organic exigencies of
the prey devoured, and the Wasp established her race; or else it was
hesitating, without determined rules, and the Wasp left no successor. In
the first case we behold innate instinct; in the second acquired habit.
A strange acquisition, truly! An acquisition presumed to be made by an
impossible creature; an acquisition supposed to develop in no less
impossible successors! Though the snow-ball, slowly rolling, at last
becomes an enormous sphere, it is still necessary that the starting-point
shall not have been NIL. The big ball implies the little ball, as small as
you please. Now, in harking back to the origin of these acquired habits, if
I interrogate the possibilities I obtain zero as the only answer. If the
animal does not know its trade thoroughly, if it has to acquire something,
all the more if it has to acquire everything, it perishes: that is
inevitable; without the little snow-ball the big snow-ball cannot be
rolled. If it has nothing to acquire, if it knows all that it needs to
know, it flourishes and leaves descendants behind it. But then it possesses
innate instinct, the instinct which learns nothing and forgets nothing, the
instinct which is steadfast throughout time.
The building up of theories has never appealed to me: I suspect them one
and all. To argue nebulously upon dubious premises likes me no better. I
observe, I experiment and I let the facts speak for themselves. We have
just heard these facts. Let each now decide for himself whether instinct is
an innate faculty or an acquired habit.
CHAPTER 4. THE CETONIA-LARVA.
The Scolia's feeding-period lasts, on the average, for a dozen days or so.
By then the victuals are no more than a crumpled bag, a skin emptied of the
last scrap of nutriment. A little earlier, the russet-yellow tint announces
the extinction of the last spark of life in the creature that is being
devoured. The empty skin is pushed back to make space; the dining-room, a
shapeless cavity with crumbling walls, is tidied up a little; and the
Scolia-grub sets to work on its cocoon without further delay.
The first courses form a general scaffolding, which finds a support here
and there on the earthen walls, and consist of a rough, blood-red fabric.
When the larva is merely laid, as required by my investigations, in a
hollow made with the finger-tip in the bed of mould, it is not able to spin
its cocoon, for want of a ceiling to which to fasten the upper threads of
its network. To weave its cocoon, every spinning larva is compelled to
isolate itself in a hammock slung in an open-work enclosure, which enables
it to distribute its thread uniformly in all directions. If there be no
ceiling, the upper part of the cocoon cannot be fashioned, because the
worker lacks the necessary points of support. Under these conditions my
Scolia-grubs contrive at most to upholster their little pit with a thick
down of reddish silk. Discouraged by futile endeavours, some of them die.
It is as if they had been killed by the silk which they omit to disgorge
because they are unable to make the right use of it. This, if we were not
watchful, would be a very frequent cause of failure in our attempts at
artificial rearing. But, once the danger has been perceived, the remedy is
simple. I make a ceiling over the cavity by laying a short strip of paper
above it. If I want to see how matters are progressing, I bend the strip
into a semicircle, into a half-cylinder with open ends. Those who wish to
play the breeder for themselves will be able to profit by these little
practical details.
In twenty-four hours the cocoon is finished; at least, it no longer allows
us to see the grub, which is doubtless making the walls of its dwelling
still thicker. At first the cocoon is a vivid red; later it changes to a
light chestnut-brown. Its form is that of an ellipsoid, with a major axis
26 millimetres in length, while the minor axis measures 11 millimetres.
(1.014 x .429 inch.--Translator's Note.) These dimensions, which
incidentally are inclined to vary slightly, are those of the female
cocoons. In the other sex they are smaller and may measure as little as 17
millimetres in length by 7 millimetres in width. (.663 x .273 inch.--
Translator's Note.)
The two ends of the ellipsoid have the same form, so much so that it is
only thanks to an individual peculiarity, independent of the shape, that we
can tell the cephalic from the anal extremity. The cephalic pole is
flexible and yields to the pressure of my tweezers; the anal pole is hard
and unyielding. The wrapper is double, as in the cocoons of the Sphex. (Cf.
"The Hunting Wasps": chapters 4 to 10 et passim.--Translator's Note.) The
outer envelope, consisting of pure silk, is thin, flexible and offers
little resistance. It is closely superimposed upon the inner envelope and
is easily separated from it everywhere, except at the anal end, where it
adheres to the second envelope. The adhesion of the two wrappers at one end
and the non-adhesion at the other are the cause of the differences which
the tweezers reveal when pinching the two ends of the cocoon.
The inner envelope is firm, elastic, rigid and, to a certain point,
brittle. I do not hesitate to look upon it as consisting of a silken tissue
which the larva, towards the end of its task, has steeped thoroughly in a
sort of varnish prepared not by the silk-glands but by the stomach. The
cocoons of the Sphex have already shown us a similar varnish. This product
of the chylific ventricle is chestnut-brown. It is this which, saturating
the thickness of the tissue, effaces the bright red of the beginning and
replaces it by a brown tint. It is this again which, disgorged more
profusely at the lower end of the cocoon, glues the two wrappers together
at that point.
The perfect insect is hatched at the beginning of July. The emergence takes
place without any violent effraction, without any ragged rents. A clean,
circular fissure appears at some distance from the top; and the cephalic
end is detached all of a piece, as a loose lid might be. It is as though
the recluse had only to raise a cover by butting it with her head, so exact
is the line of division, at least as regards the inner envelope, the
stronger and more important of the two. As for the outer wrapper, its lack
of resistance enables it to yield without difficulty when the other gives
way.
I cannot quite make out by what knack the Wasp contrives to detach the cap
of the inner shell with such accuracy. Is it the art practised by the
tailor when cutting his stuff, with mandibles taking the place of scissors?
I hardly venture to admit as much: the tissue is so tough and the circle of
division so precise. The mandibles are not sharp enough to cut without
leaving a ragged edge; and then what geometrical certainty they would need
for an operation so perfect that it might well have been performed with the
compasses!
I suspect therefore that the Scolia first fashions the outer sac in
accordance with the usual method, that is, by distributing the silk
uniformly, without any special preparation of one part of the wall more
than of another, and that it afterwards changes its method of weaving in
order to attend to the main work, the inner shell. In this it apparently
imitates the Bembex (Cf. "The Hunting Wasps": chapters 14 to 16.--
Translator's Note.), which weaves a sort of eel-trap, whose ample mesh
allows it to gather grains of sand outside and encrust them one by one in
the silky network, and completes the performance with a cap fitting the
entrance to the trap. This provides a circular line of least resistance,
along which the casket breaks open afterwards. If the Scolia really works
in the same manner, everything is explained: the eel-trap, while still
open, enables it to soak with varnish both the inside and the outside of
the inner shell, which has to acquire the consistency of parchment; lastly,
the cap which completes and closes the structure leaves for the future a
circular line capable of splitting easily and neatly.
This is enough on the subject of the Scolia-grub. Let us go back to its
provender, of whose remarkable structure we as yet know nothing. In order
that it may be consumed with the delicate anatomical discretion imposed by
the necessity of having fresh food to the last, the Cetonia-grub must be
plunged into a state of absolute immobility: any twitchings on its part--as
the experiments which I have undertaken go to prove--would discourage our
nibbling larva and impede the work of carving, which has to be effected
with so much circumspection. It is not enough for the victim to be unable
to move from place to place beneath the soil: in addition to this, the
contractible power in its sturdy muscular organism must be suppressed.
In its normal state, this larva, at the very least disturbance, curls
itself up, almost as the Hedgehog does; and the two halves of the ventral
surface are laid one against the other. You are quite surprised at the
strength which the creature displays in keeping itself thus contracted. If
you try to unroll it, your fingers encounter a resistance far greater than
the size of the animal would have caused you to suspect. To overcome the
resistance of this sort of spring coiled upon itself, you have to force it,
so much so that you are afraid, if you persist, of seeing the indomitable
spiral suddenly burst and shoot forth its entrails.
A similar muscular energy is found in the larvae of the Oryctes (Also known
as the Rhinoceros Beetle.--Translator's Note.), the Anoxia (A Beetle akin
to the Cockchafer.--Translator's Note.), the Cockchafer. Weighed down by a
heavy belly and living underground, where they feed either on leaf-mould or
on roots, these larvae all possess the vigorous constitution needed to drag
their corpulence through a resisting medium. All of them also roll
themselves into a hook which is not straightened without an effort.
Now what would become of the egg and the new-born grub of the Scoliae,
fixed under the belly, at the centre of the Cetonia's spiral, or inside the
hook of the Oryctes or the Anoxia? They would be crushed between the jaws
of the living vice. It is essential that the arc should slacken and the
hook unbend, without the least possibility of their returning to a state of
tension. Indeed, the well-being of the Scoliae demands something more:
those powerful bodies must not retain even the power to quiver, lest they
derange a method of feeding which has to be conducted with the greatest
caution.
The Cetonia-grub to which the Two-banded Scolia's egg is fastened fulfils
the required conditions admirably. It is lying on its back, in the midst of
the mould, with its belly fully extended. Long accustomed though I be to
this spectacle of victims paralysed by the sting of the Hunting Wasp, I
cannot suppress my astonishment at the profound immobility of the prey
before my eyes. In the other victims with flexible skins, Caterpillars,
Crickets, Mantes, Ephippigers, I perceived at least some pulsations of the
abdomen, a few feeble contortions under the stimulus of a needle. There is
nothing of the sort here, nothing but absolute inertia, except in the head,
where I see, from time to time, the mouth-parts open and close, the palpi
give a tremor, the short antennae sway to and fro. A prick with the point
of a needle causes no contraction, no matter what the spot pricked. Though
I stab it through and through, the creature does not stir, be it ever so
little. A corpse is not more inert. Never, since my remotest
investigations, have I witnessed so profound a paralysis. I have seen many
wonders due to the surgical talent of the Wasp; but to-day's marvel
surpasses them all.
I am doubly surprised when I consider the unfavourable conditions under
which the Scolia operates. The other paralysers work in the open air, in
the full light of day. There is nothing to hinder them. They enjoy full
liberty of action in seizing the prey, holding it in position and
sacrificing it; they are able to see the victim and to parry its means of
defence, to avoid its spears, its pincers. The spot or spots to be attained
are within their reach; they drive the dagger in without let or hindrance.
What difficulties, on the other hand, await the Scolia! She hunts
underground, in the blackest darkness. Her movements are laboured and
uncertain, owing to the mould, which is continually giving way all round
her; she cannot keep her eyes on the terrible mandibles, which are capable
of cutting her body in two with a single bite. Moreover, the Cetonia-grub,
perceiving that the enemy is approaching, assumes its defensive posture,
rolls itself up and makes a shield for its only vulnerable part, the
ventral surface, with its convex back. No, it cannot be an easy operation
to subdue the powerful larva in its underground retreat and to stab with
the precision which immediate paralysis requires.
We wish that we might witness the struggle between the two adversaries and
see at first hand what happens, but we cannot hope to succeed. It all takes
place in the mysterious darkness of the soil; in broad daylight, the attack
would not be delivered, for the victim must remain where it is and then and
there receive the egg, which is unable to thrive and develop except under
the warm cover of vegetable mould. If direct observation is impracticable,
we can at least foresee the main outlines of the drama by allowing
ourselves to be guided by the warlike manoeuvres of other burrowers.
I picture things thus: digging and rummaging through the heap of mould,
guided perhaps by that singular sensibility of the antennae which enables
the Hairy Ammophila to discover the Grey Worm (The caterpillar of the
Turnip Moth. Cf. "The Hunting Wasps": chapters 18 to 20.--Translator's
Note.) underground, the Scolia ends by finding a Cetonia-larva, a good
plump one, in the pink of condition, having reached its full growth, just
what the grub which is to feed on it requires. Forthwith, the assaulted
victim, contracting desperately, rolls itself into a ball. The other seizes
it by the skin of the neck. To unroll it is impossible to the insect, for I
myself have some trouble in doing so. One single point is accessible to the
sting: the under part of the head, or rather of the first segments, which
are placed outside the coil, so that the grub's hard cranium makes a
rampart for the hinder extremity, which is less well defended. Here the
Wasp's sting enters and here only can it enter, within a narrowly
circumscribed area. One stab only of the lancet is given at this point, one
only because there is no room for more; and this is enough: the larva is
absolutely paralysed.
The nervous functions are abolished instantly; the muscular contractions
cease; and the animal uncoils like a broken spring. Henceforth motionless,
it lies on its back, its ventral surface fully exposed from end to end. On
the median line of this surface, towards the rear, near the brown patch due
to the alimentary broth contained in the intestine, the Scolia lays her egg
and without more ado, leaves everything lying on the actual spot where the
murder was committed, in order to go in search of another victim.
This is how the deed must be done: the results prove it emphatically. But
then the Cetonia-grub must possess a very exceptional structure in its
nervous organization. The larva's violent contraction leaves but a single
point of attack open to the sting, the under part of the neck, which is
doubtless uncovered when the victim tries to defend itself with its
mandibles; and yet a stab in this one point produces the most thorough
paralysis that I have ever seen. It is the general rule that larvae possess
a centre of innervation for each segment. This is so in particular with the
Grey Worm, the sacrificial victim of the Hairy Ammophila. The Wasp is
acquainted with this anatomical secret: she stabs the caterpillar again and
again, from end to end, segment by segment, ganglion by ganglion. With such
an organization the Cetonia-grub, unconquerably coiled upon itself would
defy the paralyser's surgical skill.
If the first ganglion were wounded, the others would remain uninjured; and
the powerful body, actuated by these last, would lose none of its powers of
contraction. Woe then to the egg, to the young grub held fast in its
embrace! And how insurmountable would be the difficulties if the Scolia,
working in the profound darkness amid the crumbling soil and confronted by
a terrible pair of mandibles, had to stab each segment in turn with her
sting, with the certainty of method displayed by the Ammophila! The
delicate operation is possible in the open air, where nothing stands in the
way, in broad daylight, where the sight guides the scalpel, and with a
patient which can always be released if it becomes dangerous. But in the
dark, underground, amidst the ruins of a ceiling which crumbles in
consequence of the conflict and at close quarters with an opponent greatly
her superior in strength, how is the Scolia to guide her sting with the
accuracy that is essential if the stabs are to be repeated?
So profound a paralysis; the difficulty of vivisection underground; the
desperate coiling of the victim: all these things tell me that the Cetonia-
grub, as regards its nervous system, must possess a structure peculiar to
itself. The whole of the ganglia must be concentrated in a limited area in
the first segments, almost under the neck. I see this as clearly as though
it had been revealed to me by a post-mortem dissection.
Never was anatomical forecast more fully confirmed by direct examination.
After forty-eight hours in benzine, which dissolves the fat and renders the
nervous system more plainly visible, the Cetonia-grub is subjected to
dissection. Those of my readers who are familiar with these investigations
will understand my delight. What a clever school is the Scolia's! It is
just as I thought! Admirable! The thoracic and abdominal ganglia are
gathered into a single nervous mass, situated within the quadrilateral
bounded by the four hinder legs, which legs are very near the head. It is a
tiny, dull-white cylinder, about three millimetres long by half a
millimetre wide. (.117 x .019 inch.--Translator's Note.) This is the organ
which the Scolia's sting must attack in order to secure the paralysis of
the whole body, excepting the head, which is provided with special ganglia.
>From it run numbers of filaments which actuate the feet and the powerful
muscular layer which is the creature's essential motor organ. When examined
merely through the pocket-lens, this cylinder appears to be slightly
furrowed transversely, a proof of its complex structure. Under the
microscope, it is seen to be formed by the close juxtaposition, the
welding, end to end, of the ganglia, which can be distinguished one from
the other by a slight intermediate groove. The bulkiest are the first, the
fourth and the tenth, or last; these are all very nearly of equal size. The
rest are barely half or even a third as large as those mentioned.
The Interrupted Scolia experiences the same hunting and surgical
difficulties when she attacks, in the crumbling, sandy soil, the larvae of
the Shaggy Anoxia or of the Morning Anoxia, according to the district; and
these difficulties, if they are to be overcome, demand in the victim a
concentrated nervous system, like the Cetonia's. Such is my logical
conviction before making my examination; such also is the result of direct
observation. When subjected to the scalpel, the larva of the Morning Anoxia
shows me its centres of innervation for the thorax and the abdomen,
gathered into a short cylinder, which, placed very far forward, almost
immediately after the head, does not run back beyond the level of the
second pair of legs. The vulnerable point is thus easily accessible to the
sting, despite the creature's posture of defence, in which it contracts and
coils up. In this cylinder I recognize eleven ganglia, one more than in the
Cetonia. The first three, or thoracic, ganglia are plainly distinguishable
from one another, although they are set very close together; the rest are
all in contact. The largest are the three thoracic ganglia and the
eleventh.
After ascertaining these facts, I remembered Swammerdam's investigations
into the grub of the Monoceros, our Oryctes nasicornis. (Jan Swammerdam
(1637-1680), the Dutch naturalist and anatomist.--Translator's Note.) I
chanced to possess an abridgement of the "Biblia naturae," the masterly
work of the father of insect anatomy. I consulted the venerable volume. It
informed me that the learned Dutchman had been struck, long before I was,
by an anatomical peculiarity similar to that which the larvae of the
Cetoniae and Anoxiae had shown me in their nerve-centres. Having observed
in the Silk-worm a nervous system formed of ganglia distinct one from the
other, he was quite surprised to find that, in the grub of the Oryctes, the
same system was concentrated into a short chain of ganglia in
juxtaposition. His was the surprise of the anatomist who, studying the
organ qua organ, sees for the first time an unusual conformation. Mine was
of a different nature: I was amazed to see the precision with which the
paralysis of the victim sacrificed by the Scolia, a paralysis so profound
in spite of the difficulties of an underground operation, had guided my
forecast as to structure when, anticipating the dissection, I declared in
favour of an exceptional concentration of the nervous system. Physiology
perceived what anatomy had not yet revealed, at all events to my eyes, for
since then, on dipping into my books, I have learnt that these anatomical
peculiarities, which were then so new to me, are now within the domain of
current science. We know that, in the Scarabaeidae, both the larva and the
perfect insect are endowed with a concentrated nervous system.
The Garden Scolia attacks Oryctes nasicornis; the Two-banded Scolia the
Cetonia; the Interrupted Scolia the Anoxia. All three operate below ground,
under the most unfavourable conditions; and all three have for their victim
a larva of one of the Scarabaeidae, which, thanks to the exceptional
arrangement of its nerve-centres, lends itself, alone of all larvae, to the
Wasp's successful enterprises. In the presence of this underground game, so
greatly varied in size and shape and yet so judiciously selected to
facilitate paralysis, I do not hesitate to generalize and I accept, as the
ration of the other Scoliae, larvae of Lamellicorns whose species will be
determined by future observation. Perhaps one of them will be found to give
chase to the terrible enemy of my crops, the voracious White Worm, the grub
of the Cockchafer; perhaps the Hemorrhoidal Scolia, rivalling in size the
Garden Scolia and like her, no doubt, requiring a copious diet, will be
entered in the insects' "Who's Who" as the destroyer of the Pine-chafer,
that magnificent Beetle, flecked with white upon a black or brown ground,
who of an evening, during the summer solstice, browses on the foliage of
the fir-trees. Though unable to speak with certainty or precision, I am
inclined to look upon these devourers of Scarabaeus-grubs as valiant
agricultural auxiliaries.
The Cetonia-larva has figured hitherto only in its quality of a paralysed
victim. We will now consider it in its normal state. With its convex back
and its almost flat ventral surface, the creature is like a semi-cylinder
in shape, fuller in the hinder portion. On the back, each of the segments,
except the last, or anal, segment, puckers into three thick pads, bristling
with stiff, tawny hairs. The anal segment, much wider than the rest, is
rounded at the end and coloured a deep brown by the contents of the
intestine, which show through the translucent skin; it bristles with hairs
like the other segments, but is level, without pads. On the ventral
surface, the segments have no creases; and the hairs, though abundant, are
rather less so than on the back. The legs, which are quite well-formed, are
short and feeble in comparison with the animal's size. The head has a
strong, horny cap for a cranium. The mandibles are powerful, with bevelled
tips and three or four teeth on the edge of the bevel.
Its mode of locomotion marks it as an idiosyncratic, exceptional, fantastic
creature, having no fellow, that I know of, in the insect world. Though
endowed with legs--a trifle short, it is true, but after all as good as
those of a host of other larvae--it never uses them for walking. It
progresses on its back, always on its back, never otherwise. By means of
wriggling movements and the purchase afforded by the dorsal bristles, it
makes its way belly upwards, with its legs kicking the empty air. The
spectator to whom these topsy-turvy gymnastics are a novelty thinks at
first that the creature must have had a fright of some sort and that it is
struggling as best it can in the face of danger. He puts it back on its
belly; he lays it on its side. Nothing is of any use; it obstinately turns
over and resumes its dorsal progress. That is its manner of travelling over
a flat surface; it has no other.
This reversal of the usual mode of walking is so peculiar to the Cetonia-
larva that it is enough in itself to reveal the grub's identity to the
least expert eyes. Dig into the vegetable mould formed by the decayed wood
in the hollow trunks of old willow-trees, search at the foot of rotten
stumps or in heaps of compost; and, if you come upon a plumpish grub moving
along on its back, there is no room for doubt: your discovery is a Cetonia-
larva.
This topsy-turvy progress is fairly swift and is not less in speed to that
of an equally fat grub travelling on its legs. It would even be greater on
a polished surface, where walking on foot is hampered by incessant slips,
whereas the numerous hairs of the dorsal pads find the necessary support by
multiplying the points of contact. On polished wood, on a sheet of paper
and even on a strip of glass, I see my grubs moving from point to point
with the same ease as on a surface of garden mould. In the space of one
minute, on the wood of my table, they cover a distance of eight inches. The
pace is no swifter on a horizontal bed of sifted mould. A strip of glass
reduces the distance covered by one half. The slippery surface only half
paralyses this strange method of locomotion.
We will now place side by side with the Cetonia-grub the larva of the
Morning Anoxia, the prey of the Interrupted Scolia. It is very like the
larva of the Common Cockchafer. It is a fat, pot-bellied grub, with a
thick, red cap on its head and armed with strong, black mandibles, which
are powerful implements for digging and cutting through roots. The legs are
sturdy and end in a hooked nail. The creature has a long, heavy, brown
paunch. When placed on the table, it lies on its side; it struggles without
being able to advance or even to remain on its belly or back. In its usual
posture it is curled up into a narrow hook. I have never seen it straighten
itself completely; the bulky abdomen prevents it. When placed on a surface
of moist sand, the ventripotent creature is no better able to shift its
position: curved into a fish-hook, it lies on its side.
To dig into the earth and bury itself, it uses the fore-edge of its head, a
sort of weeding-hoe with the two mandibles for points. The legs take part
in this work, but far less effectually. In this way it contrives to dig
itself a shallow pit. Then, bracing itself against the wall of the pit,
with the aid of wriggling movements which are favoured by the short, stiff
hairs bristling all over its body, the grub changes its position and
plunges into the sand, but still with difficulty.
Apart from a few details, which are of no importance here, we may repeat
this sketch of the Anoxia-grub and we shall have, if the size be at least
quadrupled, a picture of the larva of Oryctes nasicornis, the monstrous
prey of the Garden Scolia. Its general appearance is the same: there is the
same exaggeration of the belly; the same hook-like curve; the same
incapacity for standing on its legs. And as much may be said of the larva
of Scarabaeus pentodon, a fellow-boarder of the Oryctes and the Cetonia.
CHAPTER 5. THE PROBLEM OF THE SCOLIAE.
Now that all the facts have been set forth, it is time to collate them. We
already know that the Beetle-hunters, the Cerceres (Cf. "The Hunting
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